<PAGE>

                                                                   Exhibit 10(g)

               CONSOLIDATED, AMENDED AND RESTATED DEED OF LEASE


     THIS CONSOLIDATED, AMENDED AND RESTATED DEED OF LEASE is made and entered
into as of the 12 day of November, 1997, effective for all purposes as of the
1st day of January, 1997, by and between (i) HMCE ASSOCIATES LIMITED
PARTNERSHIP, R.L.L.P., a Virginia registered limited partnership, successor in
interest to HMCE Associates Limited Partnership (hereinafter re(Pounds)erred to
as "Landlord"), and (ii) ICF KAISER HUNTERS BRANCH LEASING, INC., a Delaware
corporation, successor in interest to ICF International, Inc. (hereinafter
referred to as "Tenant"), and referred to by singular pronouns of the neuter
gender, regardless of the number and gender of the parties involved.

     WHEREAS, the Landlord and Tenant are parties to a certain Lease Agreement
dated January 30, 1987 (the "Lease"), pursuant to which Landlord leased to
Tenant certain office space containing approximately 196,749 square feet of net
rentable area in the office building known as "Hunter's Branch - Phase I" and
located in Fairfax, Virginia (the "Building"); and

     WHEREAS, Landlord and Tenant entered into a First Amendment to Lease
Agreement dated August 31, 1987 (the "First Amendment"), wherein Landlord leased
to Tenant certain additional space in the Building containing, in the aggregate,
approximately 3,210 square feet of net rentable area; and

     WHEREAS, Landlord and Tenant entered into a Second Amendment to Lease
Agreement dated September 23, 1987 (the "Second Amendment"), for the purpose of
complying with the requirements of Landlord's first Mortgagee; and

     WHEREAS, Landlord and Tenant entered into a Third Amendment to Lease
Agreement dated February 12, 1990 (the "Third Amendment"), which modified
certain provisions of the Lease relating to Basic Rent and Operating Expense
Increases; and

     WHEREAS, Landlord and Tenant now desire to consolidate, amend and restate
the Lease, the First Amendment, the Second Amendment and the Third Amendment in
this Consolidated, Amended and Restated Lease Agreement.

     NOW, THEREFORE, in consideration of the mutual promises hereinafter set
forth and other good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, Landlord hereby leases to Tenant, and Tenant
hereby leases from Landlord, the Leased Premises, for the Term (as defined
below), except that Landlord reserves and Tenant shall have no right in and to
(a) the use of the exterior faces of all perimeter walls of the Building, (b)
except as otherwise provided in Section 10(d), the use of the roof of the
Building, or (c) the use of the air space above the Building.

     1.   Definitions.

          (a)  General Interpretive Principles.  For purposes of this Lease,
except as otherwise expressly provided or unless the context otherwise requires,
(i) the terms defined in this Section have the meanings assigned to them in this
Section and include the plural as well as the singular, and the use of any
gender herein shall be deemed to include the other genders; (ii) accounting
terms not otherwise defined herein have the meanings assigned to them in
accordance with generally accepted accounting principles; (iii) references
herein to "Sections," "subsections," "paragraphs" and other subdivisions without
reference to a document are to designated Sections, subsections, paragraphs and
other subdivisions of this Lease; (iv) a reference to a sub-section without
further reference to a Section is a reference to such subsection as contained in
the same Section in which the reference appears, and this rule shall also apply
to paragraphs and other subdivisions; (v) the words "herein," "hereof,"
"hereunder" and other words of similar import refer to this Lease as a whole and
not to any particular provision; and (vi) the word "including" means "including,
but not limited to."
<PAGE>

          (b)  Special Lease Definitions.  As used in this Lease the following
words and phrases shall have the meanings indicated:

               Basic Rent:  For each Lease Year, an amount equal to the product
obtained by multiplying the Rentable Area of the Leased Premises by the Rent per
Square Foot for such Lease Year.

               Building: The office building known as the "ICF Kaiser Building,"
located at 9300 Lee Highway, Fairfax, Virginia 22031, on the land described in
Exhibit A to this Lease, including Tenant's non-exclusive right in and to the
parking deck and Landlord's leasehold estate in the underlying land.

               Building Rentable Area: 201,929 square feet.

               Comparison Month:  The calendar month of March.

               CPI: The Consumer Price Index for All Urban Consumers (CPI-U) --
All Items (1982-84 = 100) for the Washington, DC - MD - VA metropolitan area
currently prepared by the Bureau of Labor Statistics of the United States
Department of Labor and published bi-monthly. If, during the Term, the CPI
ceases to be published, then Landlord and Tenant shall mutually agree upon a
substitute index, it being understood and agreed that such substitute index
shall be similar index generally recognized as authoritative, and the parties
shall reconcile the base thereof with the base of the CPI. If the parties cannot
agree upon a substitute index, then the matter shall be submitted to arbitration
under the rules of the American Arbitration Association.

               First Rental Period: As defined in (S)4.2(b) of the Ground Lease.

               Inflation Adjustment:  For the sixth Lease Year (i.e. commencing
November 1, 2003) and each Lease Year thereafter during the Term (including any
Renewal Period), the lesser of (i) 2.5% of the Rent per Square Foot for the
immediately preceding Lease Year or (ii) 225% of the percentage (if any) by
which (x) the CPI for the Comparison Month in the immediately preceding Lease
Year exceeds (y) the CPI for the Comparison Month in 1998.  Exhibit C contains
an illustration of the operation of the Inflation Adjustment.

               Initial Term: The period commencing on the Lease Commencement
Date and ending on October 31, 2012, but in any event the Initial Term shall end
on any date when this Lease is sooner terminated pursuant to its terms.

               Land: The land described in Exhibit A.

               Landlord's Notice Address: 1355 Piccard Drive, Suite 470,
Rockville, Maryland 20850.

               Lease Commencement Date: January 1, 1997.

               Leased Premises: The space containing 199,959 square feet of
Rentable Area , consisting of the part of the Second Floor outlined on the floor
plans of the Building attached hereto as Exhibit B, the entire First Floor, the
entire Third through Twelfth Floors inclusive, and the Penthouse.

               Leasing Broker: The Carey Winston Company, which broker shall be
paid by Tenant.

               Office Park: The project consisting of the Building, the office
building known as 9302 Lee Highway, Fairfax, Virginia 22031, and the common
areas and facilities serving both such buildings.

               Office Space: The portion of the Building consisting of the First
through Twelfth Floors, inclusive.

                                      -2-
<PAGE>

               Operating Expense Base: The quotient obtained by dividing (i)
$1,162,899.00, by (ii) the Building Rentable Area.

               Operating Expense Commencement Date: January 1, 1998.

               Operating Expense Increases: For the calendar year in which the
Operating Expense Commencement Date occurs and each calendar year thereafter
during the Term, an amount equal to Tenant's Proportionate Share of the excess
of Landlord's Operating Expenses for such calendar year over the product
obtained by multiplying the Operating Expense Base by the Building Rentable
Area.

               Renewal Period: The additional period of five years for which
Tenant is permitted to extend the Initial Term of this Lease pursuant to Section
30.

               Rent Commencement Date: January 1, 1997.

               Rent per Square Foot: $24.00 during the period from January 1,
1997 through November 11, 1997 (i.e., total Basic Rent for such period shall be
$4,141,616.55). $24.50 for the period from November 12, 1997 through December
31, 1997, and for each of the second, third, fourth and fifth Lease Years (i.e.,
Basic Rent for such period shall be $4,898,995.50 per Lease Year). For the sixth
Lease Year, the Rent per Square Foot shall be an amount equal to $24.00,
increased by the Inflation Adjustment for the sixth Lease Year. For the seventh
Lease Year, and for each Lease Year thereafter during the Term, the Rent per
Square Foot shall be an amount equal to the Rent per Square Foot for the
immediately preceding Lease Year, increased by the Inflation Adjustment for the
Lease Year for which the computation is being made. The foregoing amounts are
net of the cost of electricity for the Leased Premises, which shall be billed to
and paid by Tenant.

               Rentable Area: The net rentable area (in square feet) of all or
any part of the Leased Premises from time to time. The net rentable area of the
Leased Premises is agreed to be 199,959 square feet.

               Second Rental Period: As defined in (S)4.2(c) of the Ground
Lease.

               Security Deposit: $125,000.

               Storage Space: The area, containing 5,855 square feet of Rentable
Area, located in the Penthouse, which is shown on the floor plans attached as
Exhibit B to this Lease.

               Tenant's Notice Address: 9300 Lee Highway, Fairfax, Virginia
22031-1207, Attn: Lease Administrator, with a copy to the same address, Attn:
General Counsel.

               Tenant's Proportionate Share: The percentage from time to time
which the Rentable Area of the Leased Premises is of the Building Rentable Area,
which percentage is acknowledged and agreed to be ninety-nine percent (99%) as
of the date of this Lease.

               Term: The Initial Term and the Renewal Period, if any, as to
which Tenant shall have effectively exercised its right to extend, but in any
event the Term shall end on any date when this Lease is sooner terminated
pursuant to the terms hereof.

          (c)  General Definitions.  As used in this Lease the following words
and phrases shall have the meanings indicated:

                                      -3-
<PAGE>

               Additional Charges: All amounts payable by Tenant to Landlord
under this Lease other than Basic Rent. All Additional Charges shall be deemed
to be additional rent and all remedies applicable to the non-payment of Basic
Rent shall be applicable thereto.

               Alterations: As defined in Section 9(a).

               Business Days: All days except Saturdays, Sundays and the
following legal holidays: New Years Day, Memorial Day, Fourth of July, Labor
Day, Thanksgiving Day and Christmas Day.

               Default Interest Rate: A rate per annum equal to the lesser of
(a) the sum of (i) the base rate of interest from time to time established and
publicly announced by NationsBank, N.A., Washington, D.C., in its sole
discretion, as its then-applicable base rate of interest to be used in
determining actual interest rates to be charged to certain of its borrowers,
said base rate to change from time to time as and when the change is announced
as being effective, plus (ii) two percent (2%), or (b) ten percent (10%) per
annum.

               Event of Default: Any of the events set forth in Section 16(a) as
an event of default.

               Floor: A floor of the Building located above the foundation slab
or above an area below grade level which is designated as a basement or cellar.
The term "Floor" preceded by a number shall mean the indicated floor of the
Building.

               Ground Lease: The Lease Agreement dated May 29, 1986, between The
First Union National Bank of Virginia, as Trustee, as successor by merger to
First American Bank of Virginia, Trustee, as lessor, and Landlord, as lessee, as
amended by a First Amendment to Ground Lease, dated August 18, 1987, and as
further amended by a Second Amendment to Ground Lease dated September 22, 1987,
pursuant to which Landlord leases the land described in Exhibit A to this Lease.

               Landlord: The landlord named herein or any subsequent owner or
lessee, from time to time, of the Landlord's interest in the Building.

               Lease: This Deed of Lease, as amended from time to time, and all
Exhibits attached hereto.

               Lease Year: The period of 12 months commencing on the Lease
Commencement Date and ending on the last day of the month which completes 12
full calendar months after the Lease Commencement Date, and each 12 month period
thereafter commencing on the first day after the end of the immediately
preceding Lease Year, except that the last Lease Year shall end on the last day
of the Term.

               Legal Requirements: All laws, statutes, ordinances, orders,
rules, regulations and requirements of all federal, state and municipal
governments, and the appropriate agencies, officers, departments, boards and
commissions thereof, and the board of fire underwriters and/or the fire
insurance rating organization or similar organization performing the same or
similar functions, whether now or hereafter in force, applicable to the Building
or any part thereof and/or the Leased Premises, and notices from Landlord's
Mortgagee, as to the manner of use or occupancy or the maintenance, repair or
condition of the Leased Premises and/or the Building, and the usual and
customary requirements of the carriers of all fire insurance policies maintained
by Landlord on the Building.

               Mortgage: Any mortgage, deed of trust or other security
instrument of record creating an interest in or affecting title to the Building
or the land on which it is constructed, or both, or any part thereof, including
a leasehold mortgage or subleasehold mortgage, and any and all renewals,
modifications, consolidations, or extensions of any such instrument; Mortgagee
shall mean the holder or beneficiary of any Mortgage.

                                      -4-
<PAGE>

               Operating Expenses: The aggregate of all costs and expenses
reasonably and customarily paid or incurred on an accrual basis by Landlord in
connection with the management, operation, servicing and maintenance of the
Leased Premises, the Building, the Building parking facility and the land on
which the Building is constructed including, but not limited to, employees'
wages, salaries, welfare and pension benefits and other fringe benefits; payroll
taxes; Real Estate Taxes; the Net Annual Rental payable by Landlord under (and
as defined in) the Ground Lease; electricity charges for the main lobby, service
areas and other common areas of the Building and the operation of the Building
elevators; telephone service; painting of public or other common areas of the
Building; exterminating service; detection and security services; trash removal;
sewer and water charges; premiums for fire and casualty, liability, rent,
workers' compensation, sprinkler, water damage and other insurance; repairs and
maintenance to the Building; building, janitorial and cleaning supplies;
uniforms and dry cleaning; snow removal; landscaping maintenance; window
cleaning; service contracts for the maintenance of elevators, boilers, HVAC and
other mechanical, plumbing and electrical equipment; legal fees (other than
legal fees relating to the negotiation of leases with present or prospective
tenants of the Building or the enforcement of Landlord's rights under leases
with tenants for space in the Building); accounting fees; advertising;
management fees of four percent (4%) of gross Building rents (exclusive of
Operating Expense payments), whether or not paid to any Person having an
interest in or under common ownership with Landlord; one-half of all costs and
expenses of providing the shuttle bus services required by Section 31 (reduced
by all amounts received by Landlord or its affiliates for after- hours shuttle
bus service); dues and assessments to any property owners' association in which
the Building is a member; window glass replacement, repair and cleaning; repair
and maintenance of the grounds, including costs of landscaping, gardening and
planting; service contracts with independent contractors, including but not
limited to security and energy management service contractors; compensation
(including employment taxes, fringe benefits, salaries, wages, medical, surgical
and general welfare benefits [including health, accident and group life
insurance]) for all personnel employed by Landlord or its property management
company who perform duties in connection with the operation, management,
maintenance and repair of the Building (in each case, allocated among all
properties served by such employees on a reasonable basis, if such employees are
utilized by more than one property), including a proportionate share of the
salary and benefits of the property manager assigned to the Building, based upon
the number of properties served by such property manager, but in no event more
than one-fourth (1/4) of such salary and benefits; and all other expenses now or
hereafter reasonably and customarily incurred in connection with the operation,
maintenance, and management of first class office buildings in the Tysons Corner
area of Northern Virginia. If Landlord makes an expenditure for a capital
improvement to the Building to reduce Operating Expenses or to comply with Legal
Requirements not in effect at the time the Building was constructed, and if,
under generally accepted accounting principles, such expenditure is not a
current expense, the cost thereof shall be amortized over a period equal to the
useful life of such improvements, determined in accordance with generally
accepted accounting principles, and the amortized cost allocated to each
calendar year during the Term shall be treated as an Operating Expense. Except
as provided in the preceding sentence, capital expenditures, depreciation and
amortization shall not be included in Operating Expenses. Refunds of Real Estate
Taxes (reduced by Landlord's reasonable expenses in obtaining such refunds),
amounts received by Landlord from tenants of the Building for after-hours
heating and air conditioning service and other special services and (to the
extent that Operating Expenses include the cost of any repair or reconstruction
work) the amount of any insurance recoveries, shall be credited against
Operating Expenses in computing the amount thereof. Operating Expenses shall
also be reduced as provided in Section 3(b). Operating Expenses shall not
include financing or mortgage costs; depreciation expense; advertising for
vacant space or building promotion; leasing commissions; executive salaries or
compensation to any employee of Landlord or its property management company
above the rank of the property manager assigned to the Building; more than one-
fourth (1/4) of the salary and benefits of the property manager assigned to the
Building; the cost of tenant improvements; legal fees for leasing vacant space
in the Building or enforcing Landlord's rights under leases with tenants for
space in the Building; or charges for electricity used directly by Tenant or by
other tenants of the Building. Operating Expenses also shall not include: costs
of additional insurance premiums for the Building due to any tenant's operations
within such tenant's demised premises, which are payable by such tenant under
such tenant's lease; the cost of repairs or replacements incurred by reason of
fire or other casualty; or any other costs or expenses for which Landlord
actually receives reimbursement from any source (other than amounts paid by
tenants of the Building with respect to Operating Expenses), including, without
limitation, insurance proceeds, condemnation awards or warranties.

                                      -5-
<PAGE>

               Penthouse: The Floor immediately above the Twelfth Floor.

               Person: A natural person, a partnership, a corporation, a limited
liability company and any other form of business or legal association or entity.

               Real Estate Taxes: All taxes, assessments, vault rentals, water
and sewer rents, if any, and other charges, if any, general, special or other
wise, including all assessments for schools, public betterments and general or
local improvements, levied or assessed upon or with respect to the ownership of
and/or all other taxable interests in the Building and the land on which it is
built imposed by any public or quasi-public authority having jurisdiction and
personal property taxes levied or assessed on Landlord's personal property used
in connection with the operation, maintenance and repair of the Building. Real
Estate Taxes shall not include any inheritance, estate, succession, transfer,
recordation, gift, franchise, corporation, income or profit tax or capital levy.
If at any time during the Term the methods of taxation shall be altered so that
in addition to or in lieu of or as a substitute for the whole or any part of any
Real Estate Taxes levied, assessed or imposed there shall be levied, assessed or
imposed (i) a tax, license fee, excise or other charge on the rents received by
Landlord, or (ii) any other type of tax or other imposition (except those
excluded from Real Estate Taxes in the preceding sentence) in lieu of, or as a
substitute for, or in addition to, the whole or any portion of any Real Estate
Taxes, then the same shall be included as Real Estate Taxes. A tax bill or true
copy thereof, together with any explanatory or detailed statement of the area or
property covered thereby, submitted by Landlord to Tenant shall be conclusive
evidence of the amount of taxes assessed or levied, as well as of the items
taxed. If any real property tax or assessment levied against the land, buildings
or improvements covered thereby or the rents reserved therefrom, shall be
evidenced by improvement or other bonds, or in other form, which may be paid in
annual installments, only the amount paid or payable in any Lease Year shall be
included as Real Estate Taxes for that Lease Year.

               Taking: A taking of property or any interest therein or right
appurtenant or accruing thereto, by condemnation or eminent domain or by action,
proceedings, or agreement in lieu thereof, pursuant to governmental authority.

               Tenant: The tenant named herein and any permitted assignee under
Section 15.

               Tenant's Special Installations: As defined in Section 9(d).

               Unavoidable Delays: Delays caused by strikes, acts of God,
lockouts, labor difficulties, riots, explosions, sabotage, accidents, inability
to obtain labor or materials, governmental restrictions, enemy action, civil
commotion, fire, unavoidable casualty or similar causes beyond the reasonable
control of the Landlord or the Tenant, as the case may be. No payment of any
monetary amounts required of, or the obtaining or delivery of any required
insurance policies by, either Landlord or Tenant shall be delayed or excused by
acts of Unavoidable Delay.

               2.   Condition of Premises.

               Tenant accepts the Leased Premises in their as-is, where-is
condition as of the date of this Lease, subject to any and all deficiencies and
defects therein, and without any express or implied warranties of habitability,
fitness, fitness for a particular purpose or otherwise.

               3.   Rent and Additional Charges.

               (a)  Payment of Rent and Additional Charges. Tenant shall pay the
Basic Rent for each Lease Year in equal monthly installments in advance on the
first (1st) day of each month during the Term. The Basic Rent and all Additional
Charges shall be paid promptly when due, in lawful money of the United States,
without notice or demand and without deduction, diminution, abatement,
counterclaim or setoff of any amount or for any reason whatsoever, except as
otherwise expressly provided in subsections (b) and (g) and Sections 13 and

                                      -6-
<PAGE>

14, to Landlord by wire transfer to such bank account as Landlord may from time
to time designate. If Tenant makes any payment to Landlord by check (which, for
any payment other than by wire transfer, shall require Landlord's consent), such
payment shall be by check of Tenant and Landlord shall not be required to accept
the check of any other person, and any check received by Landlord shall be
deemed received subject to collection. If any check is mailed by Tenant, Tenant
shall post such check in sufficient time prior to the date when payment is due
so that such check will be received by Landlord on or before the date when
payment is due. Tenant shall assume the risk of lateness or failure of delivery
of the mails, and no lateness or failure of the mails will excuse Tenant from
its obligation to have made the payment in question when required under this
Lease. All bank service charges resulting from any bad checks shall be borne by
Tenant. The rent reserved under this Lease shall be the total of all Basic Rent
and Additional Charges, increased and adjusted as elsewhere herein provided,
payable during the entire Term and, accordingly, the methods of payment provided
for herein, namely, annual and monthly rental payments, are for convenience only
and are made on account of the total rent reserved hereunder.

               (b)  Payment of Operating Expense Increases.  Tenant shall pay as
additional rent Operating Expense Increases for each calendar year, commencing
with the calendar year in which the Operating Expense Commencement Date occurs.
Landlord shall make a reasonable estimate of Tenant's Operating Expense
Increases for each calendar year (based on the projected Real Estate Taxes
payable for the real estate tax fiscal years included in such calendar year, the
other Operating Expenses for the preceding calendar year and known increases in
other Operating Expenses for the current calendar year), and Tenant shall pay to
Landlord 1/12th of the amount so estimated on the first day of each month in
advance, beginning on January 1, 1998 and continuing thereafter throughout the
Term.  If Landlord's estimate of Tenant's Operating Expense Increases for any
calendar year is received by Tenant after January 1 of the calendar year, Tenant
shall pay to Landlord in a lump sum, within 15 days after receipt of the
estimate, the arrearages in the monthly estimates for each month in the calendar
year before receipt of the estimate and shall pay the remaining monthly
installments on the first day of each month in advance during the balance of the
calendar year.  Within 150 days after the end of each calendar year, Landlord
shall submit to Tenant a statement prepared by an independent certified public
accountant setting forth in reasonable detail the Operating Expenses for such
calendar year and the amount of Tenant's Operating Expense Increases for such
calendar year.  If Tenant's Operating Expense Increases so stated are more than
the amount theretofore paid by Tenant for Operating Expense Increases based on
Landlord's estimate, Tenant shall pay to Landlord the deficiency within 15 days
after the submission of such statement.  If Tenant's Operating Expense Increases
so stated are less than the amount theretofore paid by Tenant for Operating
Expense Increases based on Landlord's estimate, Landlord shall refund to Tenant
the excess within 15 days after submission of such statement or Landlord, at its
option, shall credit the excess against the next monthly installment of Basic
Rent thereafter payable by Tenant under this Lease.  Tenant, at its sole cost
and expense, shall have the right, at reasonable times and upon reasonable
notice given within 90 days after receipt of a statement for Tenant's Operating
Expense Increases for any calendar year, to audit the statements furnished to
Tenant for such calendar year.  If either the Operating Expense Commencement
Date shall not coincide with the beginning of a calendar year or the last day of
the Term shall not coincide with the end of a calendar year, then the amount of
Operating Expense Increases payable for the calendar year in which the Operating
Expense Commencement Date or the last day of the Term occurs, as the case may
be, shall be pro-rated on a daily basis between Landlord and Tenant based on the
number of days in such calendar year after the Operating Expense Commencement
Date or before the last day of the Term.  Tenant's obligations under this
subsection to pay Operating Expense Increases and Landlord's obligation to
reimburse Tenant for an overpayment of Operating Expenses shall survive the
expiration of the Term.

               (c)  Interest.  If Tenant fails to make any payment of Basic Rent
or Additional Charges by the earlier to occur of (i) 5 business days after the
due date thereof or (ii) 7 days after the due date thereof, interest shall, at
Landlord's option, accrue on the unpaid portion thereof from the due date at the
Default Interest Rate, but in no event at a rate higher than the maximum rate
allowed by law, and shall be payable on demand.

               (d)  Accord and Satisfaction.  No payment by Tenant or receipt by
Landlord of any lesser amount than the amount stipulated to be paid hereunder
shall be deemed other than on account of the earliest

                                      -7-
<PAGE>

stipulated Basic Rent or Additional Charges; nor shall any endorsement or
statement on any check or letter be deemed an accord and satisfaction, and
Landlord may accept any check or payment without prejudice to Landlord's right
to recover the balance due or to pursue any other remedy available to Landlord.

               (e)  Late Payment Charge. If Tenant fails to pay any Basic Rent
or Additional Charges by the earlier to occur of (i) 5 business days after the
due date thereof or (ii) 7 days after the due date thereof, Tenant shall also
pay to Landlord on demand a late payment service charge (to cover Landlord's
administrative and overhead expenses of processing late payments) equal to the
greater of $100.00 or 5% of such unpaid sum for each and every calendar month or
part thereof after the due date that such sum has not been paid to Landlord.
Such payment shall be deemed liquidated damages and not a penalty, but shall not
excuse the untimely payment of rent.

               (f)  Reduction of Real Estate Taxes. Landlord shall give Tenant a
copy of any tax assessment notice with respect to the Building within 15 days
after receipt thereof. Landlord will use reasonable efforts to obtain a
reduction of Real Estate Taxes, provided Tenant makes a written request to
Landlord so to do and, in such request, agrees to pay its proportionate share of
the costs thereof as hereinafter provided, and Landlord receives such request
not less than 20 days prior to the last day on which Real Estate Tax reduction
proceedings for the particular real estate tax year in question may be
commenced. The method and manner of conducting proceedings for such reduction,
including the selection of counsel, shall be solely within the judgment and
determination of Landlord, and Landlord may cancel, discontinue or settle such
proceedings if, in Landlord's judgment, such cancellation, discontinuance or
settlement is advisable. Landlord shall keep Tenant informed of the status of
any such proceeding. If Landlord determines to cancel or discontinue such
proceeding, Tenant shall have the right, either alone or with other tenants of
the Building, to continue such proceeding at its or their own expense. To the
extent that the reasonable costs and expenses, including legal fees, of such
proceedings instituted and conducted by Landlord, requested by Tenant and
others, exceed the amount of any tax refund, Tenant shall pay that proportion of
such excess cost and expense which the Rentable Area of the Leased Premises
bears to the total rentable area leased to all tenants making such request at
the time it is made.

               (g)  Abatement of Basic Rent. If, because of Landlord's failure
to provide any of the services referred to in Sections 5(h), all or
substantially all of the Leased Premises becomes untenantable and Tenant is
unable to and does not, in fact, use all or substantially all of the Leased
Premises for the uses permitted by Section 6(a) for a continuous period of 10
Business Days, then provided the cause of such cessation of services is not the
result, in whole or in principal part, of Tenant's negligence or intentional
misconduct, Tenant shall be entitled to an abatement of Basic Rent for the
period of time in which Tenant is unable to use, and does not, in fact, use all
or substantially all of the Leased Premises for the uses permitted by Section
6(a). Any dispute between Landlord and Tenant as to Tenant's entitlement to an
abatement of Basic Rent shall be submitted to mediation pursuant to Section 28.

               (h)  Retroactive Rent Adjustment. Subject to the availability of
Net Cash Flow, as defined in Section 2.2 of the Limited Liability Company
Agreement of Hunters Branch Partners, L.L.C., reduced only by the Retroactive
Rent Adjustments described herein and in Tenant's Lease for premises in 9302 Lee
Highway, Vienna, Virginia ("Available Cash Flow"), Tenant shall receive
Retroactive Rent Adjustments in the following amounts for the following 12-month
periods ("Adjustment Years") during the Term:

<TABLE>
<CAPTION>
                 Adjustment Year      Amount of Rent Adjustment
               <S>                    <C>
               11/1/97 - 10/31/98            $269,455.00
               11/1/98 - 10/31/99             274,042.00
               11/1/99 - 10/31/00             287,035.00
               11/1/00 - 10/31/01             307,856.00
               11/1/01 - 10/31/02             319,547.00
               11/1/02 - 10/31/03             206,425.00
</TABLE>

                                      -8-
<PAGE>

<TABLE>
               <S>                            <C>
               11/1/03 - 10/31/04             216,051.00
               11/1/04 - 10/31/05             236,776.00
               11/1/05 - 10/31/06             240,617.00
               11/1/06 - 10/31/07             153,560.00
               11/1/07 - 10/31/08             262,733.00
               11/1/08 - 10/31/09             263,676.00
               11/1/09 - 10/31/10             298,457.00
               11/1/10 - 10/31/11             351,375.00
               11/1/11 - 10/31/12             379,037.00
</TABLE>

               Subject to Available Cash Flow, the Retroactive Rent Adjustment
shall be paid by Landlord to Tenant in equal monthly installments in arrears. If
the monthly installment of the Retroactive Rent Adjustment for any month is not
fully paid because of the lack of Available Cash Flow, then the unpaid portion
shall be paid in a later month of the Term (if any) when there is sufficient
Available Cash Flow to pay such unpaid portion. Landlord agrees that it will not
pay, and Tenant agrees that it will not accept, a Retroactive Rent Adjustment
for any month during any Adjustment Year unless the Annual Priority Return (as
defined in Section 2.2 of the Limited Liability Company Agreement of Hunters
Branch Partners, L.L.C.) for such month (together with accrued interest, if any)
has been paid by Hunters Branch Partners, L.L.C. to the Person entitled to
receive such payment.

               (i)  Lease Restructuring Fee.  Upon execution of this Lease,
Tenant has paid Landlord a Lease Restructuring Fee in the amount of $660,767.80,
receipt of which is hereby acknowledged by Landlord.

               4.   Common Areas.

               Throughout the Term, Tenant and its agents, employees and
business invitees shall have the non-exclusive right, in common with other
tenants of the Building and the adjacent office building, to use the public
lobbies, elevators, corridors, stairways, parking garage, sky walk, patios,
sidewalks, roadways and other common areas in the Building and the Land, and the
toilet rooms in public areas of multi-tenant floors in the Building. Landlord
shall have the right to rent parking spaces in the parking garage to persons
other than tenants of the Building and the adjacent office building with
Tenant's prior written approval, which approval shall not be unreasonably
withheld, and which approval shall be deemed given provided that (i) no third
party parking contract shall be for a period of more than one (1) month, (ii)
access to the parking garage shall be controlled by access or key cards, and
(iii) reasonable security shall be provided with respect to the parking garage
area. Landlord shall have the right at any time, without the Tenant's consent,
to change the arrangement or location of entrances, passageways, doors,
doorways, corridors, stairs, toilet rooms or other public portions of the
Building, provided any such change does not unreasonably obstruct Tenant's
access to the Leased Premises. The balconies on the tenth, eleventh and twelfth
floors of the Building shall be reserved for Tenant's exclusive use.
Notwithstanding anything to the contrary in this Lease, tenants of the other
building in the Office Park (9302 Lee Highway), their agents, employees and
business invitees will not have any right to use the internal lobbies,
elevators, corridors, stairways and toilet rooms in the Building.

               5.   Services and Utilities.

               (a)  Building Services.  Throughout the Term, Landlord agrees
that the Building will be managed and maintained in accordance with generally
accepted industry practices and in a manner befitting a modern, first class
rental office building in Fairfax County, Virginia, and that, subject to Legal
Requirements, it will furnish to Tenant the following services:

               (1)  Subject to the provisions of subsection (b), normal and
usual electricity for lighting purposes and the operation of ordinary office
equipment;

                                      -9-
<PAGE>

               (2)  Adequate supplies for toilet rooms located in public areas
of the Building;

               (3)  Normal and usual cleaning and janitorial services after
business hours on Business Days in accordance with the standards set forth in
Exhibit D attached hereto and made a part hereof, provided, however, that
Landlord shall not provide cleaning and janitorial services to the double-
secured areas of the Leased Premises;

               (4)  Hot and cold running water in the toilet rooms located in
public areas of the Building and at valved outlets at the locations in the
Leased Premises shown on Tenant's Space Layout;

               (5)  Subject to the provisions of subsections (c) and (e),
heating and air-conditioning to the Leased Premises when required for the
comfortable occupancy of the Leased Premises, at reasonable temperatures,
pressures and degrees of humidity, and in reasonable volumes and velocities,
between the hours of 8:00 A.M. and 7:00 P.M. on Business Days and between the
hours of 9:00 A.M. and 1:00 P.M. on Saturdays unless Saturday is a legal
holiday;

               (6)  Automatically operated elevator facilities 24 hours a day,
seven days a week throughout the Term;

               (7)  All electric bulbs and fluorescent tubes in permanently
installed light fixtures in the Leased Premises and in the public areas of the
Building;

               (8)  Five (5) keys for the suite entry door to each portion of
the Leased Premises located on a separate Floor at no cost to Tenant, but all
additional keys, including replacements for lost keys, shall be issued only upon
the payment of a reasonable cost for each additional key;

               (9)  An electronic card security access system for the public
areas of the Building and the garage and a reasonable number of access cards for
use by Tenant's employees; and

               (10) A fully-operational structured parking facility for use by
tenants of the Building with access limited to Persons authorized by Tenant or
Landlord.

               (b)  Electricity.  Landlord shall not be liable in any way to
Tenant for any failure or defect in the supply or character of electrical energy
furnished to the Leased Premises by reason of any requirement, act or omission
of the public utility serving the Building with electricity. Tenant's use of
electrical energy in the Leased Premises shall not at any time exceed the
capacity of any of the electrical conductors and equipment in or otherwise
serving the Leased Premises as shown on Landlord's Building Plans. Tenant shall
not install or operate in the Leased Premises any electrically operated
equipment which uses electric current in excess of the capacity of the feeders
and panel boards serving the Leased Premises as shown on Landlord's Building
Plans without Landlord's written consent, which consent may be conditioned upon
Tenant's agreement to pay the cost of any additional wiring which may be
required for the operation of such equipment. In order to insure that such
capacity is not exceeded and to avert a possible adverse effect upon the
Building electrical service Tenant shall give notice to Landlord whenever Tenant
shall connect to the Building electrical distribution system any electrically
operated equipment other than lamps, typewriters and similar small office
machines. Any feeders or risers to supply Tenant's electrical requirements in
addition to those originally installed, and all other equipment proper and
necessary in connection with such feeders or risers, shall be installed by
Landlord upon Tenant's request, at the sole cost and expense of Tenant, provided
that, in Landlord's reasonable judgment, such additional feeders or risers are
permissible under applicable laws and insurance regulations and the installation
of such feeders or risers will not cause permanent damage or injury to the
Building or cause or create a dangerous condition or unreasonably interfere with
other tenants of the Building. All Floors occupied entirely by Tenant shall be
separately metered or sub-metered for electricity and all other parts of the
Leased Premises, may, at Landlord's option, be separately

                                      -10-
<PAGE>

metered or sub-metered for electricity. Tenant shall pay (or reimburse Landlord
for) the cost of purchasing and installing separate electric meters or sub-
meters for each whole Floor and each part of a Floor included in the Leased
Premises, and for any other part of the Leased Premises which Landlord elects to
have metered or sub-metered. Tenant shall pay directly to the public utility
company all charges for electricity used by Tenant in all parts of the Leased
Premises which are separately metered, or Tenant shall reimburse Landlord
directly for its electrical usage in all parts of the Leased Premises which are
sub-metered. Landlord shall have the right from time to time to have a survey
made by an independent electrical engineer or electrical consulting firm to be
selected and paid for by Landlord to determine the amount of electricity
consumed by Tenant in the parts of the Leased Premises which do not consist of
an entire Floor. Tenant shall pay to Landlord, at monthly intervals upon receipt
of an invoice therefor, the cost of electricity it consumes in the parts of the
Leased Premises which do not consist of an entire Floor as determined by such
electrical engineer or consulting firm.

               (c)  Heating and Air-Conditioning.  Landlord shall provide heat
and air-conditioning at times in addition to those specified in paragraph (5) of
subsection (a) at Tenant's expense, provided Tenant gives Landlord notice prior
to 3:00 P.M. (in the case of after-hours service on weekdays) and prior to 3:00
P.M. on Fridays or the day preceding a holiday (in the case of after-hours
service on Saturdays, Sundays or holidays).

               (d)  Maintenance of Pipes, Conduits, etc.  Landlord reserves the
right to erect, use, maintain and repair pipes, conduits, cables, plumbing,
vents and wires in, to and through the Leased Premises as and to the extent that
Landlord may now or hereafter deem to be necessary or appropriate for the proper
operation and maintenance of the Building, or other tenants' installations in
the Building, and the right at all times to transmit water, heat, air-
conditioning and electric current through such pipes, conduits, cables,
plumbing, vents and wires, provided that Landlord, in the exercise of such
rights, shall not unreasonably inconvenience Tenant or unreasonably interfere
with Tenant's use of the Leased Premises.

               (e)  HVAC Specifications.  Landlord agrees that the air-
conditioning system in the portion of the Leased Premises consisting of Office
Space will be capable of providing, and (unless otherwise ordered by federal,
state or local governmental authorities) the system shall provide, temperatures
of not more than 77 degrees F dry bulb and a relative humidity not in excess of
50% with outside conditions of 95 degrees F dry bulb and 78 degrees F wet bulb,
except as otherwise provided in this subsection. Landlord agrees that the
heating system in the portion of the Leased Premises consisting of Office Space
will be capable of providing, and (unless otherwise ordered by federal, state or
local governmental authorities) the system shall provide, temperatures of not
less than 70 degrees F whenever the outdoor dry bulb temperature is lower than
65 degrees F but no lower than 0 degrees F, with indoor relative humidity at
such level as not to permit the formation of condensation on the windows.
Landlord shall not be responsible if the normal operation of the Building air-
conditioning system shall fail to provide conditioned air at reasonable
temperatures, pressures or degrees of humidity or in reasonable volumes or
velocities in any portions of the Leased Premises consisting of Office Space
which (i) shall have a connected electrical load in excess of three watts per
square foot of Rentable Area of the Leased Premises for all purposes (including
lighting and power) or which shall have a human occupancy factor in excess of
one person for each 100 square feet of Rentable Area of the portion of the
Leased Premises consisting of Office Space (the average electrical load and
human occupancy factors for which the Building air-conditioning system is
designed), or (ii) because of rearrangement of partitioning or other Alterations
made by or on behalf of Tenant or any Person claiming through or under Tenant
(excepting work performed by Landlord for Tenant prior to Tenant's initial
occupancy of the Leased Premises).

               (f)  Access to HVAC Facilities.  Landlord shall have unrestricted
access to any and all air-conditioning facilities in the Leased Premises for the
purposes of repairs, maintenance, alterations and improvements, but in
exercising its rights under this subsection Landlord shall use its best efforts
to minimize interference with Tenant's business in the Leased Premises.
Notwithstanding anything to the contrary herein or in Section 5(d), except in
the event of an emergency, Landlord may obtain access to the double-secured
areas of the Leased Premises only with the permission and assistance of Tenant's
Director of Facilities or his designee.  Tenant shall provide Landlord with keys
to the double-secured areas of the Leased Premises.  Tenant's Director of
Facilities, or his designee, shall be available to provide access to the double-
secured areas of the Leased Premises on

                                      -11-
<PAGE>

a non-emergency basis promptly after Landlord's request for permission to enter
the same, and in any event no later than 24 hours after such request.

               (g)  Reduction of Air-Conditioning Use.  Tenant agrees to use
reasonable efforts to keep or cause to be kept closed all window draperies or
venetian blinds in the Leased Premises as and when necessary because of the
sun's position whenever the air-conditioning system is in operation, and Tenant
agrees at all times to cooperate fully with Landlord and to abide by all the
reasonable regulations and requirements which Landlord may prescribe for the
proper functioning and protection of the Building air-conditioning system.

               (h)  Cessation of HVAC and Mechanical Services.  Landlord
reserves the right to stop the service of heating, air-conditioning,
ventilating, elevator, plumbing, electricity or other mechanical systems or
facilities in the Building, if necessary by reason of accident or emergency, or
for repairs, alterations, replacements, additions or improvements which, in the
reasonable judgment of Landlord, are desirable or necessary, until said repairs,
alterations, replacements, additions or improvements shall have been completed.
The exercise of such right by Landlord shall not constitute an actual or
constructive eviction, in whole or in part, or relieve Tenant from any of its
obligations under this Lease, or impose any liability upon Landlord or its
agents by reason of inconvenience or annoyance to Tenant, or injury to, or
interruption of, Tenant's business, or otherwise, or entitle Tenant to any
abatement or diminution of rent except as provided in Section 3(i). Except in
cases of emergency repairs, Landlord will give Tenant reasonable advance notice
of any contemplated stoppage of any such systems or facilities pursuant to the
foregoing. In all cases, Landlord will use due diligence to complete any such
repairs, alterations, replacements, additions or improvements promptly. Landlord
shall also perform any such work in a manner designed to minimize interference
with Tenant's normal business operations.

               6.   Use of Leased Premises.

               (a)  Permitted Uses.  Tenant shall use and occupy the portion of
the Leased Premises consisting of Office Space solely for general office
purposes, and shall use and occupy the portion of the Leased Premises consisting
of Storage Space solely for storage, all in accordance with the applicable
zoning regulations and consistent with the character and dignity of the
Building, and shall not use, permit or suffer the use of the Leased Premises for
any other purpose whatsoever without the prior written consent of the Landlord.
Tenant shall not use, or permit the Leased Premises to be used, for the sale of
food, beverages or tobacco products, except that Tenant may operate on the
Leased Premises vending machines for the sale of food, beverages and tobacco
products to its employees. Tenant shall not permit or suffer the Leased Premises
to be occupied by anyone other than Tenant except as provided by Section 15.
Tenant shall at all times have access to the Leased Premises 24 hours a day,
seven days a week, subject, however, in all respects to all the terms, covenants
and conditions contained in this Lease. However, Landlord may regulate and
restrict access to the Building at times other than normal business hours on
Business Days for security purposes so long as Tenant's employees and agents
have reasonable access to the Leased Premises without unreasonable
inconvenience.

               (b)  Restrictions on Use.  Throughout the Term, Tenant covenants
and agrees: (i) to pay 10 days before delinquency any and all taxes, assessments
and public charges levied, assessed or imposed upon Tenant's business conducted
in the Leased Premises, upon the leasehold estate created by this Lease or upon
Tenant's fixtures, furnishings or equipment in the Leased Premises; (ii) not to
use or permit or suffer the use of any portion of the Leased Premises for any
unlawful purpose; (iii) not to use the plumbing facilities for any purpose other
than that for which they were constructed, or dispose of any foreign substances
therein; (iv) not to place a load on any floor exceeding the floor load per
square foot which such floor was designed to carry in accordance with Landlord's
Building Plans, and not to install, operate or maintain in the Leased Premises
any heavy item of equipment except in such manner as to achieve a proper
distribution of weight; (v) not to strip, overload, damage or deface the Leased
Premises, or the hallways, stairways, elevators, parking facilities or other
public areas of the Building, or the fixtures therein or used therewith; (vi)
not to move any furniture or equipment into or out of the Leased Premises except
at such times as Landlord may from time to time reasonably designate; (vii) not
to use any floor adhesive in the installation of any carpeting; (viii) not to
install any other equipment of any kind or nature

                                      -12-
<PAGE>

which will or may necessitate any changes, replacements or additions to, or in
the use of, the water system, heating system, plumbing system, air-conditioning
system or electrical system of the Leased Premises or the Building, without
first obtaining the written consent of Landlord; and (ix) at all times to comply
with all Legal Requirements.

               (c)  Compliance with Legal Requirements.  Tenant will not use or
occupy the Leased Premises in violation of any Legal Requirements. If any
governmental authority, after the commencement of the Term, shall contend or
declare that the Leased Premises are being used for a purpose which is in
violation of any Legal Requirements, then Tenant shall, upon five days' notice
from Landlord, immediately discontinue such use of the Leased Premises. If
thereafter the governmental authority asserting such violation threatens,
commences or continues criminal or civil proceedings against Landlord for
Tenant's failure to discontinue such use, in addition to any and all rights,
privileges and remedies given to Landlord under this Lease for default therein,
Landlord shall have the right to terminate this Lease forthwith. Tenant shall
indemnify and hold Landlord harmless from and against any and all liability for
any such violation or violations.

               (d)  Compliance with Insurance Requirements.  Tenant shall not do
any act, matter, thing or failure to act in respect of the Leased Premises
and/or the Building that will invalidate or be in conflict with fire insurance
policies covering the Building or any part thereof, and shall not do, or permit
anything to be done, in or upon the Leased Premises and/or the Building, or
bring or keep anything therein, which shall increase the rate of fire insurance
on the Building or on any property located therein. If, by reason of the failure
of Tenant to comply with the provisions of this subsection, the fire insurance
rate shall at any time be higher than it otherwise would be, then Tenant shall
reimburse Landlord and any other tenant of the Building, on demand, for that
part of all premiums for any insurance coverage that shall have been charged
because of such violation by Tenant and which Landlord or such other tenant, or
both, shall have paid on account of an increase in the rate or rates in its own
policies of insurance. Tenant shall not be responsible for any increase in fire
insurance rates generally applicable to office space in Fairfax County,
Virginia, and not resulting from the particular manner in which Tenant uses the
Leased Premises.

               (e)  No Flammable Substances.  Tenant shall not bring or permit
to be brought or kept in or on the Leased Premises any flammable, combustible or
explosive fluid, material, chemical or substance except standard cleaning fluid,
standard equipment and materials (including magnetic tape) customarily used in
conjunction with business machines and equipment of the type used from time to
time by Tenant in reasonable quantities.

               7.   Care of Leased Premises.

               (a)  By Tenant.  Tenant shall act with care in its use and
occupancy of the Leased Premises and the fixtures therein and, at Tenant's sole
cost and expense, shall make all repairs and replacements to the Leased
Premises, structural or otherwise, necessitated or caused by the acts, omissions
or negligence of Tenant or any Person claiming through or under Tenant or by the
use or occupancy or manner of use or occupancy of the Leased Premises by Tenant
or any such Person; however the foregoing provisions of this subsection shall be
subject to the provisions of Section 13. Without affecting Tenant's obligations
set forth in the preceding sentence, Tenant, at Tenant's sole cost and expense,
shall also (i) make all repairs and replacements, as and when necessary, to
Tenant's Special Installations and to any Alterations made or performed by or on
behalf of Tenant or any Person claiming through or under Tenant, (ii) perform
all maintenance and make all repairs and replacements, as and when necessary, to
any air-conditioning equipment, private elevators, escalators, conveyors or
mechanical systems (other than the standard equipment and systems serving the
Building) which may be installed in the Leased Premises, or elsewhere in the
Building and serving the Leased Premises, by Landlord, Tenant or others, (iii)
perform all maintenance and make all repairs and replacements, as and when
necessary, to the antennas and satellite dishes installed by Tenant on the roof
of the Building and make all repairs to the roof caused by such installation,
and (iv) perform regular cleaning and janitorial services in the double-secured
areas of the Leased Premises. However, except as otherwise provided in this
Lease, Tenant shall not have any right to install air-conditioning equipment,
elevators, escalators, conveyors or mechanical systems. In addition to the
foregoing, all damage or injury to the

                                      -13-
<PAGE>

Leased Premises and to its fixtures, appurtenances and equipment or to the
Building or to its fixtures, appurtenances and equipment caused by Tenant moving
property in or out of the Building or by installation or removal of furniture,
fixtures or other property by Tenant shall be repaired, restored or replaced
promptly by Tenant, at its sole cost and expense, to the reasonable satisfaction
of Landlord. All such aforesaid repairs, restoration and replacements shall be
in quality and class equal to the original work or installation but in no event
need exceed Building standards.

               (b)  By Landlord.  Except as otherwise provided in subsection
(a), Landlord shall perform the following maintenance and repairs as and when
necessary (the costs of which shall be Operating Expenses hereunder, to the
extent included in the definition of Operating Expenses in Section 1(c)): (i)
structural repairs to the Leased Premises and Building; (ii) maintenance and
repairs required in order to provide the elevator, plumbing, electrical, heating
and air-conditioning services to be furnished by Landlord pursuant to this
Lease; (iii) maintenance of and repairs to exterior portions of the Building,
including the windows, balconies and roof thereof; (iv) maintenance of and
repairs to the toilet rooms in the Building, and to the public lobbies,
elevators, corridors, stairways, parking garage, sky walk, patios, sidewalks,
roadways and other common areas in the Building and the Land; and (v) other
repairs to the Leased Premises and the Building necessary for Tenant's use and
enjoyment of the Leased Premises. Landlord's obligations to make repairs to the
Leased Premises under the preceding sentence shall not accrue until after notice
to Landlord of the necessity for any specific repair.

               8.   Rules and Regulations.

               Tenant and its agents and employees shall comply with and observe
all reasonable rules and regulations concerning the use, management, operation,
safety and good order of the Leased Premises and the Building which may from
time to time be promulgated by Landlord, provided that such rules and
regulations are not inconsistent with the provisions of this Lease and do not
materially interfere with Tenant's use of the Leased Premises. Initial rules and
regulations, which shall be effective until amended by Landlord, are attached to
this Lease as Exhibit E hereto and made a part hereof. Tenant shall be deemed to
have received notice of any amendment to the rules and regulations when a copy
of such amendment has been delivered to Tenant at the Leased Premises or has
been mailed to Tenant in the manner prescribed for the giving of notices. If
Tenant disputes the reasonableness of any additional rule or regulation
hereafter made or adopted by Landlord, the parties agree to submit the question
of the reasonableness of such rule or regulation for decision to the governing
board for the time being of the Building Owners and Managers Association of
Washington, D.C., or to such impartial person or persons as it or the parties
hereto may designate, whose determination shall be final and conclusive upon the
parties hereto. Tenant may not dispute the reasonableness of any additional rule
or regulation unless Tenant's intention to do so shall be asserted by notice
given to Landlord within 15 days after notice is given to Tenant of the adoption
of any such additional rule or regulation. Landlord shall not be responsible to
Tenant for any violation of the rules and regulations, or the covenants or
agreements contained in any other lease, by any other tenant of the Building, or
such tenant's agents or employees, and Landlord may waive in writing, or
otherwise, any or all of the rules or regulations in respect of any one or more
tenants.

               9.   Tenant's Alterations and Installments.

               (a)  Restrictions on Alterations. Tenant shall not make or
perform, or permit the making or performance of, any alterations, installations,
improvements, additions or other physical changes in or about the Leased
Premises (referred to collectively as "Alterations") without Landlord's prior
consent. Landlord agrees not unreasonably to withhold or delay its consent to
any nonstructural Alterations proposed to be made by Tenant to adapt the Leased
Premises for Tenant's business purposes or the business purposes of any other
permitted occupant of the Leased Premises, except that Landlord shall have no
obligation to consent to any Alteration which will reduce the value or utility
of the Building or affect the outside appearance of the Building or the color or
style of any venetian blinds supplied by Landlord (except that Tenant may remove
any such venetian blinds provided Tenant promptly replaces such venetian blinds
with venetian blinds of a similar type and color). Notwithstanding the foregoing
provisions of this subsection or Landlord's consent to any Alterations, all
Alterations, whether made

                                      -14-
<PAGE>

prior to or during the Term, shall be made and performed in conformity with and
subject to the following provisions: (i) all Alterations shall be made and
performed at Tenant's sole cost and expense and at such time and in such manner
as Landlord may reasonably from time to time designate; (ii) Alterations shall
be made only by contractors or mechanics approved by Landlord, such approval not
to be unreasonably withheld or delayed; (iii) no Alteration shall materially
affect any part of the Building other than the Leased Premises or adversely
affect any service required to be furnished by Landlord to Tenant or to any
other tenant or occupant of the Building; (iv) all business machines and
mechanical equipment shall be placed and maintained by Tenant in settings
sufficient in Landlord's reasonable judgment to absorb and prevent vibration,
noise and annoyance to other tenants or occupants of the Building; (v) Tenant
shall submit to Landlord reasonably detailed plans and specifications for each
proposed alteration and shall not commence any such Alteration without first
obtaining Landlord's approval of such plans and specifications, which approval
will not be unreasonably withheld or delayed; (vi) all Alterations in or to the
electrical facilities in or serving the Leased Premises shall be subject to the
provisions of Section 5 relating to exceeding electrical capacity; (vii)
notwithstanding Landlord's approval of plans and specifications for any
Alteration, all Alterations shall be made and performed in full compliance with
all Legal Requirements and in accordance with the Rules and Regulations; (viii)
all materials and equipment to be incorporated in the Leased Premises as a
result of all Alterations shall be of good quality; and (ix) Tenant shall
require any contractor performing Alterations to carry and maintain at all times
during the performance of the work, at no expense to Landlord, (i) a policy of
comprehensive public liability insurance, including contractor's liability
coverage, contractual liability coverage, completed operations coverage,
contractor's protective liability coverage and a broad form property damage
endorsement, naming Landlord and (at Landlord's request) any Mortgagee of the
Building and any management agent as additional named insureds), with such
policy to afford protection to the limit of not less than $2,000,000 with
respect to bodily injury or death to any number of persons in any one accident
and to the limit of not less than $1,000,000 to damage to the property of any
one owner from one occurrence, and (ii) workers' compensation or similar
insurance in the form and amounts required by the laws of the State of Virginia.
In the event the estimated cost of an Alteration (which shall include the
aggregate cost of a series of Alterations which are reasonably aggregated into a
single project) is in excess of $100,000.00, or in the event of an Alteration to
a structural member of, or mechanical system in, the Leased Premises, Landlord
shall have the right to place other and further restrictions and conditions
thereon prior to Tenant being authorized to commence such Alteration. Such
additional conditions may include, by way of illustration and not of limitation,
the requirement that the contractor be bonded or bondable. In the event of any
dispute between the parties as to whether or not Landlord has acted reasonably
in any case with respect to which Landlord is required, pursuant to the
provisions of this subsection (a), to do so, Tenant's sole remedy shall be to
submit such dispute to mediation pursuant to Section 28. If the determination in
any such mediation shall be adverse to Landlord, Landlord nevertheless shall not
be liable to Tenant for breach of Landlord's covenant to act reasonably, and
Tenant's sole remedy in such event shall be to proceed with the proposed
Alterations. However, if the parties are unable to settle such matter by
mediation, and such matter is submitted to litigation, Landlord's liability and
Tenant's remedies shall not be so limited.

               (b)  Tenant's Right to Cure. If Tenant shall be in default under
this Section by reason of the making of any Alteration not hereby authorized or
by reason of failure to give any notice or to obtain any approval required
herein, Tenant may cure such default within the applicable grace period provided
in this Lease for curing such default by removing such Alteration and restoring
the Leased Premises to their former condition, as provided in Section 7.

               (c)  Fixtures Become Landlord's Property.  Except to the extent
specifically provided in subsection (e), all appurtenances, fixtures,
improvements, additions and other property attached to or installed in the
Leased Premises, whether by Landlord or Tenant or others, and whether at
Landlord's expense, or Tenant's expense, or the joint expense of Landlord and
Tenant, which are of a permanent nature or which cannot be removed without
structural damage to the Building, shall be and remain the property of Landlord.
Any replacements of any property of Landlord, whether made at Tenant's expense
or otherwise, shall be and remain the property of Landlord.

                                      -15-
<PAGE>

               (d)  Tenant's Special Installations.  All furniture, furnishings
and trade fixtures, excepting lighting fixtures and equipment, but including,
without limitation, murals, carpets, rugs, business machines and equipment,
vaults, vault doors and door frames, and vault equipment, if any, safe deposit
equipment, counterscreens, grillwork, cages, partitions which are moveable,
railings, raised floors, escalators, conveyors, stairs, elevators, paneling,
equipment relating to food preparation, food storage and serving, dishwashing
and cleaning devices and air-conditioning equipment, and any other moveable
property installed by, or at the expense of Tenant, including any such property
paid for with any allowance provided by Landlord to Tenant, shall remain the
property of Tenant and are referred to herein as "Tenant's Special
Installations". Tenant may at its expense remove any part of said property at
any time during the Term, and shall at its expense remove all of said property
at the expiration or other termination of the Term unless Landlord shall
otherwise consent in writing. Upon removal of any or all of said property Tenant
shall then repair all damage caused by such removal. Any of Tenant's Special
Installations which are not removed from the Leased Premises at the expiration
of the Term shall be deemed to have been abandoned by Tenant and may be disposed
of by Landlord without liability to Tenant.

               (e)  Mechanics' Liens.  Notice is hereby given that Landlord
shall not be liable for any labor or materials furnished or to be furnished to
Tenant upon credit, and that no mechanic's, materialman's or other lien for any
such labor or materials shall attach to or affect the reversion or other estate
or interest of Landlord in and to the Leased Premises or the Building. Whenever
and as often as any mechanic's lien or materialman's lien shall have been filed
against the Leased Premises or the Building based upon any act or interest of
Tenant or of anyone claiming through Tenant, or if any lien or security interest
with respect thereto shall have been filed affecting any materials, machinery or
fixtures used in the construction, repair or operation thereof or annexed
thereto by Tenant or its successors in interest, Tenant shall forthwith take
such action by bonding, deposit or payment as will remove or satisfy the lien or
other security interest and in default thereof after the expiration of 20 days
after notice to Tenant, Landlord, in addition to any other remedy under this
Lease, may pay the amount secured by such lien or security interest or discharge
the same by deposit and the amount so paid or deposited shall be collectible as
additional rent. The provisions of this subsection shall not be applicable to
liens filed with respect to work done for Tenant's account by Landlord.

               10.  Name of Building; Tenant's Signs.

               (a)  Name.  Provided that no Event of Default (as defined in
Section 16) or Event of Bankruptcy (as defined in Section 17) has occurred and
is continuing, throughout the Term, the Building shall be designated as the "ICF
Kaiser Building", and Landlord shall use that name in all advertising prepared
by, or at the direction of, Landlord in connection with the leasing of space in
the Building to the public. Notwithstanding the foregoing, if Tenant shall
change its corporate name, then Tenant shall have the right, by written notice
to Landlord, to require Landlord to re-designate the Building with a name
incorporating all or part of Tenant's new name, provided the same is not in
violation of any rule, regulation or statute having jurisdiction over the
Building or Landlord. In such event, Tenant shall bear all costs of changing the
signage on the Building, and Tenant shall, within fifteen (15) days after
receipt of an invoice therefor, reimburse Landlord for Landlord's reasonable
costs incurred in connection with the Building name change, including costs
incurred to change Landlord's advertising and costs of any required notices to
any governmental agencies. Landlord expressly reserves the right to have the
Building designated by a street number or numbers and to affix to the Building,
at locations designated by Landlord, signs indicating any such number or numbers
and the name of the Building (if any) as selected from time to time by Tenant in
accordance with the provisions of this subsection.

               (b)  Restrictions on Exterior Signs.  Except as otherwise
provided in subsection (d), Landlord has not granted to Tenant any rights in or
to the roof or the outer side of the outside walls of the Building, control of
which is hereby reserved by Landlord. Tenant shall not display or erect any
lettering, signs, advertisements, awnings or other projections on the exterior
of the Leased Premises or in the interior of the Leased Premises if visible from
a public way, except for customary hallway door lettering.

                                      -16-
<PAGE>

               (c)   Directory Tablets.  Landlord, at its expense, shall
maintain the existing directory tablets (i) in the main lobby of the other
building in the Office Park, (ii) in the skywalk between the Building and the
other building in the Office Park (located at 9302 Lee Highway), and (iii) on
the walkway between the Building and the other building in the Office Park, upon
each of which Landlord, at Tenant's expense, will affix Tenant's name and a
reasonable number of names of its officers, partners or employees. The size,
color and style of such directories and names affixed thereto shall be selected
by Landlord.

               (d)   Tenant's Permitted Signs.  Subject to Section 10(a) above,
Landlord shall permit Tenant throughout the Term to install and maintain,
subject to Legal Requirements, two suitable signs on the exterior of the
Building.  The location, size, color and style of Tenant's exterior signs shall
be subject to Landlord's approval, such approval not to be unreasonably withheld
or delayed.  Landlord hereby approves Tenant's signs which are currently on the
Building, and agrees that, if the name of the Building is changed pursuant to
Section 10(a), Tenant, at its expense, may replace such signs with similar signs
displaying the new name.

               (e)   Access to Roof.  Throughout the Term, Landlord shall permit
Tenant to install and maintain, subject to Legal Requirements and the provisions
of this Section 10(e), not more than three (3) satellite or antenna dishes on
the roof of the Building ("Tenant's Roof Use").

               (i)   Landlord shall make available to Tenant access to and
locations mutually acceptable to Landlord and Tenant on the roof for the
construction, installation, maintenance, repair, operation and use of such
satellite or antenna dishes. Tenant shall screen such installations in a manner
mutually acceptable to Landlord and Tenant. Tenant shall have the right to
remove such satellite or antenna dishes and any related equipment from the
Building at the expiration or other termination of the Term of this Lease,
provided that Tenant repairs any damage occasioned by such removal. Tenant shall
pay all costs associated with the installation, maintenance, repair, use,
insurance and removal of such satellite or antenna dishes and any related
equipment.

               (ii)  Tenant shall give Landlord's Building manager reasonable
telephonic notice before any entry onto the roof of the Building by Tenant's
agents, employees or contractors, and shall permit Landlord's Building manager
to accompany Tenant's agents, employees or contractors on any such entry onto
the roof.  Except as otherwise hereinafter set forth in this Section 10(e),
Landlord shall not be liable for any claims, losses, actions, damages,
liabilities or expenses arising from any satellite or antenna dishes or related
equipment installed by Tenant on the roof of the Building, or the installation,
maintenance, repair, use or removal of such dishes and related equipment, unless
caused by the negligence or willful misconduct of Landlord, its agents,
employees or contractors.

               (iii) If Landlord permits any other party to install satellite or
antenna dishes on the roof of the Building, and such equipment interferes with
the operation of Tenant's equipment, then Landlord, at its expense, shall take
whatever measures may be necessary to eliminate such interference.

               (iv)  If the rate of any insurance carried by Landlord is
increased as a result of Tenant's Roof Use, then Tenant will pay to Landlord
within ten (10) days before the date Landlord is obligated to pay a premium on
the insurance (or within ten (10) days after Landlord delivers to Tenant a
certified statement from Landlord's insurance carrier stating that the rate
increase was caused by Tenant's Roof Use, whichever date is later), a sum equal
to the difference between the original premium and the increased premium
resulting from Tenant's Roof Use.

               (v)   Landlord has not made any representations or promises
pertaining to the suitability of the Building's roof for Tenant's Roof Use.
Tenant, solely for the purpose of this Section 10(e) and its right to rooftop
access hereunder, accepts the rooftop in its "as is" condition.

               (vi)  Tenant will obtain prior to installation, any and all
governmental licenses, approvals necessary for the installation, maintenance and
use of any equipment installed pursuant to this Section

                                      -17-
<PAGE>

10(e). Tenant's Roof Use shall not in any way conflict with any applicable Legal
Requirements. Tenant shall indemnify and hold Landlord harmless from and against
any and all loss, cost (including reasonable attorney's fees incurred in
defending Landlord), damage or liability arising out of any violation by
Tenant's Roof Use of any applicable Legal Requirements.

               (vii)  Tenant's Roof Use shall be exercised: (1) in such manner
as will not create any hazardous condition or interfere with or impair the
operation of the heating, ventilation, air conditioning, plumbing, electrical,
fire protection, life, safety, public utilities or other systems or facilities
in the Building; (2) in compliance with all applicable Legal Requirements; (3)
in such a manner as will not unreasonably interfere with Landlord's operation or
maintenance of the Building; (4) at Tenant's cost, including the cost of
repairing any damage to the Building and any personal injury and/or property
damage caused by the installation, inspection, adjustment, maintenance, removal
or replacement of any of Tenant's equipment on the roof; and (5) in a manner
which will not void or invalidate any roof warranty then in effect with respect
to the roof of the Building. Tenant's Roof Use shall be used solely in the
ordinary course of Tenant's business operations (and not for resale by Tenant),
and any use of the roof outside of the ordinary course of Tenant's business
operations (such as, but not limited to, subleasing portions of the roof for
profit to third parties, in order for such third parties to establish
communications transmission facilities) shall be subject to Landlord's consent,
which consent shall not be unreasonably withheld, but may be conditioned, inter
alia, upon the payment by Tenant to Landlord of any net revenues paid to Tenant
in respect thereof.

               11.  Liability Insurance.

               (a)  Required Coverage.  Tenant, at Tenant's sole cost and
expense, shall obtain and maintain in effect at all times during the Term, a
policy of comprehensive general public liability insurance with broad form
property damage endorsement, naming Landlord and (at Landlord's request) any
Mortgagee of the Building and any management agent as additional insured(s),
protecting Landlord, Tenant and any such Mortgagee and management agent against
any liability for bodily injury, death or property damage occurring upon, in or
about any part of the Building, including the roof, or the Land, the Leased
Premises or any appurtenances thereto, with such policies to afford protection
to the limit of $5,000,000 with respect to bodily injury or death to any one
person, to the limit of $5,000,000 with respect to bodily injury or death to any
number of persons in any one accident, and to the limit of $5,000,000 with
respect to damage to the property of any one owner from one occurrence. Such
comprehensive liability insurance may be effected by a policy or policies of
blanket insurance which cover other property in addition to the Leased Premises,
provided that the protection afforded thereunder shall be no less than that
which would have been afforded under a separate policy or policies relating only
to the Leased Premises and provided further that in all other respects any such
policy shall comply with the other provisions of this Section.

               (b)  Policy Requirements.  The insurance policy required to be
obtained by Tenant under this Section: (i) shall be issued by insurance
companies rated A- or better in the most current issue of Best's Insurance
Reports, licensed to do business in the state in which the Building is located
and domiciled in the United States; and (ii) shall be written as primary policy
coverage and not contributing with or in excess of any coverage which Landlord
may carry. Neither the issuance of any insurance policy required under this
Lease, nor the minimum limits specified herein with respect to Tenant's
insurance coverage, shall be deemed to limit or restrict in any way Tenant's
liability arising under or out of this Lease. With respect to each insurance
policy required to be obtained by Tenant under this Section, on or before the
Lease Commencement Date, and at least 30 days before the expiration of the
expiring policy or certificate previously furnished, Tenant shall deliver to
Landlord a certificate of insurance therefor, together with evidence of payment
of all applicable premiums. Each insurance policy required to be carried
hereunder by or on behalf of Tenant shall provide (and any certificate
evidencing the existence of each such insurance policy shall certify) that such
insurance policy shall not be canceled unless Landlord shall have received 20
days' prior written notice of cancellation.

               (c)  Indemnification of Landlord.  Except for the willful or
negligent acts or omissions of Landlord or its agents or employees, Tenant
hereby agrees to indemnify and hold harmless Landlord

                                      -18-
<PAGE>

from and against any and all claims, losses, actions, damages, liabilities and
expenses (including attorneys' fees) that (i) arise from or are in connection
with Tenant's possession, use, occupancy, management, repair, maintenance or
control of the Leased Premises, or any portion thereof, or (ii) arise from or
are in connection with any willful or negligent act or omission of Tenant or
Tenant's agents, employees or subtenants, or (iii) result from any default,
breach, violation or nonperformance of this Lease or any provision therein by
Tenant, or (iv) arise from injury or death to persons or damage to property
sustained on or about the Leased Premises, or (v) arise from Tenant's
installation, maintenance, repair, use or removal of any rooftop satellite or
antenna dishes or related equipment. Tenant shall, at its own cost and expense,
defend any and all actions, suits and proceedings which may be brought against
Landlord with respect to the foregoing or in which Landlord may be impleaded.
Tenant shall pay, satisfy and discharge any and all money judgments which may be
recovered against Landlord in connection with the foregoing.

               (d)  Indemnification of Tenant.  Except for the willful or
negligent acts or omissions of Tenant or its agents or employees, Landlord
hereby agrees to indemnify and hold harmless Tenant from and against any and all
claims, losses, actions, damages, liabilities and expenses (including attorneys'
fees) that (i) arise from or are in connection with Landlord's possession, use,
occupancy, management, repair, maintenance or control of the common areas of the
Building located on any Floor not wholly occupied by Tenant, or (ii) arise from
or are in connection with any willful or negligent act or omission of Landlord
or Landlord's agents or employees, or (iii) result from any default, breach,
violation or nonperformance of this Lease or any provision therein by Landlord,
or (iv) arise from injury or death to persons or damage to property sustained on
or about the common areas of the Building located on any Floor not wholly
occupied by Tenant. Landlord shall, at its own cost and expense, defend any and
all actions, suits and proceedings which may be brought against Tenant with
respect to the foregoing or in which Tenant may be impleaded. Landlord shall
pay, satisfy and discharge any and all money judgments which may be recovered
against Tenant in connection with the foregoing.

               12.  Fire Insurance.

               (a)  Required Coverage.  Landlord shall, throughout the Term, at
its expense, keep the Building, but not Tenant's Special Installations,
Alterations or Tenant's furniture, furnishings, trade fixtures or property
removable by Tenant under the provisions of this Lease (including any rooftop
satellite or antenna dishes and related equipment), insured against all loss or
damage by fire with extended coverage in such amount as any first Mortgagee of
the Building may from time to time require. Tenant shall, throughout the Term,
at its expense, keep Tenant's Special Installations and Alterations and Tenant's
personal property, including any rooftop satellite or antenna dishes and related
equipment, insured against all loss or damage by fire with extended coverage in
an amount sufficient to prevent Tenant from becoming a co-insurer. Tenant's
policies of insurance shall contain, if available from the insurer, an
appropriate clause or endorsement under which the insurer agrees that such
policy shall not be canceled without at least 30 days notice to Landlord.

               (b)  Notice of Insurance Coverage.  Landlord and Tenant will (i)
if requested, advise the other as to the provisions of fire and extended
coverage insurance policies obtained pursuant to this Section, and (ii) notify
the other promptly of any change in the terms of any such policy which would
affect such provisions.

               (c)  Mutual Waiver of Subrogation

               (i)  Notwithstanding anything to the contrary in this Lease,
whether the loss or damage is due to the negligence of Landlord or Landlord's
agents or employees, or any other cause, Tenant hereby releases Landlord and
Landlord's agents and employees from responsibility for and waives its entire
claim of recovery for (i) any and all loss or damage to the personal property of
Tenant located in the Building (excluding any personal property required to be
insured by Landlord pursuant to the provisions hereof), arising out of any of
the perils which are covered by Tenant's property insurance policy, with
extended coverage endorsements which Tenant is required to obtain under the
applicable provisions of this Lease, whether or not actually obtained.

                                      -19-
<PAGE>

               (ii)  Notwithstanding anything to the contrary in this Lease,
whether the loss or damage is due to the negligence of Tenant or Tenant's agents
or employees, or any other cause, Landlord hereby releases Tenant and Tenant's
agents and employees from responsibility for and waives its entire claim of
recovery for any and all loss or damage to the Building or any personal property
of Landlord located about the Building and the Building generally and all
property attached thereto (excluding any such property required to be insured by
Tenant hereunder), arising out of any of the perils which are covered by
Landlord's property insurance policy which Landlord is required to obtain under
the applicable provisions of this Lease, whether or not actually obtained.

               (iii) Landlord and Tenant shall each cause its respective
property insurance carrier(s) to consent to such waiver of all rights of
subrogation against the other, and to issue an endorsement to all policies of
property insurance obtained by such party confirming that the foregoing release
and waiver will not invalidate such policies.

               13.   Damage by Fire or Other Casualty.

               In the event of loss of, or damage to, the Leased Premises or the
Building by fire or other casualty, the rights and obligations of the parties
hereto shall be as follows:

               (a)   Repair of Damage.  If the Leased Premises or any part
thereof shall be damaged by fire or other casualty, Tenant shall give prompt
notice thereof to Landlord, and Landlord, upon receiving such notice, shall
proceed promptly and with reasonable diligence, subject to Unavoidable Delays,
to repair, or cause to be repaired, such damage in a manner designed to minimize
interference with Tenant's occupancy (but with no obligation to employ labor at
overtime or other premium pay rates). If the Leased Premises or any part thereof
shall be rendered untenantable by reason of such damage, whether to the Leased
Premises or the Building, the Basic Rent and Additional Charges shall
proportionately abate with respect thereto for the period from the date of such
damage to the date when such damage shall have been repaired for the portion of
the Leased Premises rendered untenantable. However, if, prior to the date when
all of such damage shall have been repaired, any part of the Leased Premises is
damaged shall be rendered tenantable and shall be used or occupied by Tenant or
any Person or Persons claiming through or under Tenant, then the amount by which
the Basic Rent and Additional Charges shall abate shall be equitably apportioned
for the period from the date of any such use.

               (b)   Termination of Lease by Landlord or Tenant.  If as a result
of fire or other casualty more than one-half (1/2) of the Building Rentable
Area is rendered untenantable, Landlord within 60 days from the date of such
fire or casualty may terminate this Lease by notice to Tenant, specifying a
date, not less than 20 nor more than 40 days after the giving of such notice, on
which the Term shall expire as fully and completely as if such date were the
date herein originally fixed for the expiration of the Term. If the Leased
Premises are damaged as a result of fire or other casualty and if the damage to
the Leased Premises (but not including Tenant's Special Installations or
Alterations) is so extensive that such damage cannot be substantially repaired
within 240 days from the date of the fire or other casualty (except for
Unavoidable Delays), either Landlord or Tenant within 30 days from the date of
such fire or other casualty may terminate this Lease by notice to the other,
specifying a date, not less than 20 nor more than 40 days after the giving of
such notice, on which the Term shall expire as fully and completely as if such
date were the date originally fixed for the expiration of the Term. If either
Landlord or Tenant terminates this Lease, the Basic Rent and Additional Charges
shall be apportioned as of the date of such fire or other casualty. If neither
Landlord nor Tenant so elects to terminate this Lease, then Landlord shall
proceed to repair the damage to the Building and the damage to the Leased
Premises (but not Tenant's Special Installations or Alterations), if any shall
have occurred, and the Basic Rent and Additional Charges shall meanwhile be
apportioned and abated all as provided in subsection (a). However, if such
damage is not repaired and the Leased Premises and the Building restored to
reasonably the same condition as they were prior to such damage within 240 days
from the date of such damage (such 240-day period to-be extended by the period
of any Unavoidable Delays), Tenant, within 30 days from the expiration of such
240-day period (as the same may be extended), may terminate this Lease by notice
to Landlord, specifying a date not more than 60 days after the giving of such
notice on which the Term shall expire as fully and completely as if such date
were the date herein originally fixed for the expiration of the Term.

                                      -20-
<PAGE>

               (c)  Termination of Lease by Landlord.  If the Leased Premises
shall be rendered untenantable to the extent of eighty percent (80%) or more by
fire or other casualty during the last six months of the Term, Landlord or
Tenant may terminate this Lease upon notice to the other party given within 90
days after such fire or other casualty specifying a date, not less than 20 days
nor more than 40 days after the giving of such notice, on which the Term shall
expire as fully and completely as if such date were the date originally fixed
for the expiration of the Term. If either Landlord or Tenant terminates this
Lease pursuant to this subsection, the Basic Rent and Additional Charges shall
be apportioned as of the date of such fire or casualty.

               (d)  Limitation on Landlord's Repair Obligation.  Landlord shall
not be required to repair or replace any of Tenant's Special Installations or
Alterations or any other personal property of Tenant and no damages,
compensation or claim shall be payable by Landlord for inconvenience, loss of
business or annoyance arising from any repair or restoration of any portion of
the Leased Premises or of the Building, but the foregoing shall not be deemed to
relieve Landlord of liability for its breach of any covenant of this Lease.

               (e)  Inapplicability of Other Laws.  The provisions of this
Section shall be considered an express agreement governing any instance of
damage or destruction of the Building or the Leased Premises by fire or other
casualty, and any law now or hereafter in force providing for such a contingency
in the absence of express agreement shall have no application.

               (f)  Landlord Released from Liability.  Notwithstanding any other
provision of this Lease, Landlord shall not be liable or responsible for, and
Tenant hereby releases Landlord and its partners, officers, directors, agents
and employees from, any and all liability or responsibility to Tenant or any
Person claiming by, through or under Tenant, by way of subrogation or otherwise,
for any injury, loss or damage to Tenant's property caused by any of the perils
insured against by the fire insurance policy with extended coverage endorsement
which is customarily issued in Fairfax County, Virginia, and Tenant shall
require its insurer(s) to include in all of Tenant's insurance policies which
could give rise to a right of subrogation against Landlord a clause or
endorsement whereby the insurer(s) shall waive any right of subrogation against
Landlord.

               (g)  Tenant Released from Liability.  Notwithstanding any other
provision of this Lease, Tenant shall not be liable or responsible for, and
Landlord hereby releases Tenant and its partners, officers, directors, agents
and employees from, any and all liability or responsibility to Landlord or any
Person claiming by, through or under Landlord, by way of subrogation or
otherwise, for any injury, loss or damage to Landlord's property caused by any
of the perils insured against by the fire insurance policy with extended
coverage endorsement which is customarily issued in Fairfax County, Virginia,
and Landlord shall require its insurer(s) to include in all of Landlord's
insurance policies which could give rise to a right of subrogation against
Tenant a clause or endorsement whereby the insurer(s) shall waive any rights of
subrogation against Tenant.

               (h)  Insurance Proceeds.  The proceeds payable under all fire and
other hazard insurance policies maintained by Landlord on the Building shall
belong to and be the property of Landlord, and Tenant shall not have any
interest in such proceeds. Tenant agrees to look to its own fire and hazard
insurance policies in the event of damage to Tenant's Special Installations or
Alterations or its personal property.

               14.  Condemnation.

               (a)  Effect of Taking.  In the event of a Taking of the whole of
the Leased Premises, this Lease shall terminate as of the date of such Taking.
If only a part of the Leased Premises shall be so taken then, except as
otherwise provided in this subsection, this Lease shall continue in force and
effect but, from and after the date of the Taking, the Basic Rent and Additional
Charges shall be reduced on the basis of the square footage of the portion of
the Leased Premises so taken. If a part of the Building shall be taken, and if
either (i) the part of the Building so taken contains more than twenty-five
percent (25%) of the Rentable Area of the Leased Premises, immediately prior to
such Taking, or (ii) in Landlord's reasonable opinion, it shall be impracticable
to continue to

                                      -21-
<PAGE>

operate the Building, then Landlord, at Landlord's option, may give to Tenant
within 60 days after the date upon which Landlord shall have received notice of
the Taking, a 30 days' notice of termination of this Lease. If a part of the
Building shall be taken, and if either (i) the part of the Building taken
contains more than thirty-five percent (35%) of the Rentable Area of the Leased
Premises immediately prior to such Taking, or (ii) by reason of such Taking, all
or substantially all of the Leased Premises becomes untenantable and Tenant is
unable and does not, in fact use all or substantially all of the Leased Premises
for the uses permitted by Section 6(a), then Tenant, at Tenant's option, may
give to Landlord within 60 days after the date upon which Tenant shall have
received notice of such Taking, a 30 days' notice of termination of this Lease.
If a 30 days' notice of termination is given by Landlord or Tenant, this Lease
shall terminate upon the expiration of the 30-day period. If this Lease is
terminated pursuant to the foregoing provisions of this subsection, then, to the
extent permitted by applicable law and such Taking, Tenant shall have access to
the Leased Premises in order to remove Tenant's Special Installations and any
other personal property then owned by Tenant and which Tenant is entitled to
remove pursuant to this Lease during the period of 30 days from the date Tenant
is permitted access therefor. If a Taking occurs which does not result in the
termination of this Lease, Landlord shall repair, alter and restore the
remaining portions of the Leased Premises to their former condition to the
extent that the same may be feasible.

               (b)  Award.  Landlord shall have the exclusive right to receive
any and all awards made for damages to the Leased Premises and the Building
accruing by reason of a Taking or by reason of anything lawfully done in
pursuance of public or other authority. Tenant hereby releases and assigns to
Landlord all of Tenant's rights to such awards, and covenants to deliver such
further assignments and assurances thereof as Landlord may from time to time
request, hereby irrevocably designating and appointing Landlord as its attorney-
in-fact to execute and deliver in Tenant's name and behalf all such further
assignments thereof. However, Tenant shall have the right to make its own claim
against the condemning authority for a separate award for the value of any of
Tenant's Special Installations and Alterations, for moving and relocation
expenses and for such business damages and/or consequential damages as may be
allowed by law which do not constitute part of the compensation for the Building
and do not diminish the amount of the award to which Landlord would otherwise be
entitled.

               15.  Assignment and Subletting.

               (a)  Subletting to ICF Kaiser International, Inc.  It is
understood and agreed that Tenant will sublet the entire Leased Premises to its
affiliate, ICF Kaiser International, Inc., for a basic rent in excess of the
Basic Rent payable hereunder. Upon the written request of Landlord or any
Mortgagee following an event of default under any loan secured by a Mortgage,
Tenant shall pay to Landlord one hundred percent (100%) of the amount of such
excess, monthly as received by Tenant from ICF Kaiser International, Inc.

               (b)  Assignment and Subletting Prohibited.  Tenant shall not
mortgage, pledge, encumber, sell, assign or transfer this Lease, in whole or in
part, by operation of law or otherwise, or sublease all or any part of the
Leased Premises, without Landlord's written consent, which consent may be
withheld for any reason whatsoever except as provided in subsection (a) and
subsection (d). In connection with any request by Tenant for such consent to
assign or sublet, Tenant shall submit to Landlord, in writing, a statement
containing the name of the proposed assignee or subtenant, such information as
to its financial responsibility and standing as Landlord may reasonably require,
and all of the terms and provisions upon which the proposed assignment or
subletting is to be made, and, unless the proposed sublet area shall constitute
the entire Leased Premises, such statement shall be accompanied by a floor plan
delineating the proposed sublet area. Any attempted transfer, assignment,
subletting, mortgaging or encumbering of this Lease in violation of the
provisions of this Section shall be void and confer no rights upon any third
person. No permitted assignment or subletting shall relieve Tenant of any of its
obligations under this Lease.

               (c)  Merger and Consolidation.  Notwithstanding the provisions of
subsection (b), Tenant shall have the privilege, without the consent of
Landlord, to assign its interest in this Lease to any corporation which is a
successor to Tenant, either by merger or consolidation, or to any corporation
which controls,

                                      -22-
<PAGE>

is controlled by, or is under common control with, the Tenant. However, no such
assignment shall be valid unless, within 10 days after the consummation thereof,
Tenant shall deliver to Landlord (i) a duplicate original instrument of
assignment in form reasonably satisfactory to Landlord, duly executed by Tenant,
and (ii) an instrument in form and substance reasonably satisfactory to
Landlord, duly executed by the assignee, in which such assignee shall agree to
observe and perform, and to be personally bound by, all of the terms, covenants
and conditions of this Lease on Tenant's part to be observed and performed,
whether or not accruing prior to or after the date of such assignment and
whether or not relating to matters arising prior to such assignment.

               (d)  Permitted Subletting.  Unless an Event of Default has
occurred and is continuing, Landlord shall not unreasonably withhold or delay
Landlord's consent to sublettings by Tenant of a part or parts of the Leased
Premises, but Landlord shall not be obligated to consent to a subletting for a
use prohibited by Section 6(a). Each such subletting shall be for undivided
occupancy by the subtenant of that part of the Floor affected thereby for the
use permitted under this Lease. Landlord may, however, withhold such consent if,
in Landlord's reasonable judgment, the proposed subtenant is not engaged in a
business consistent with the character and dignity of the Building, or will
impose any additional material burden upon Landlord in the operation of the
Building (to an extent greater than the burden to which Landlord would have been
put if Tenant continued to use, or used, such part of the Leased Premises for
its own purposes). In the event of any dispute between Landlord and Tenant as to
the reasonableness of Landlord's refusal to consent to any subletting such
dispute shall be submitted to mediation pursuant to Section 28. Except as
otherwise set forth in subsection (a), if any portion of the Leased Premises is
sublet at any time, and if the rent received by Tenant on account of such
subletting exceeds the Basic Rent, allocated to the space subject to the
sublease in the proportion of the area of such space to the Rentable Area of the
Leased Premises, plus actual out-of-pocket expenses incurred by Tenant in
connection with Tenant's subleasing of such space, including advertising,
attorneys' fees, brokerage commissions and the unamortized cost of preparing
such space for occupancy by the subtenant, then, except as otherwise provided in
the next sentence, Tenant shall pay to Landlord fifty percent (50%) of such
excess, monthly as received by Tenant from the subtenant. Except as otherwise
set forth in subsection (a), Landlord shall not share in any profit derived by
Tenant from the permitted subletting of all or any part of the space located on
the Floor designated by Tenant as its "Sublet Floor" in a notice given to
Landlord before Tenant enters into its first permitted sublease pursuant to this
subsection. Notwithstanding anything to the contrary in this Section 15(d),
Tenant shall have the right to sublet space in the Leased Premises to Tenant's
affiliates (hereinafter defined), subcontractors or consultants without notice
to or the consent of Landlord, and, except as set forth in Section 15(a),
without paying any portion of the profits of such subletting to Landlord. As
used herein, a "Tenant's affiliate" shall mean a corporation or other entity
which controls, is controlled by or is under common control with Tenant, or
which is a joint venture partner of Tenant.

               (e)  Collection of Rent from Assignee.  If Tenant's interest in
this Lease is assigned, whether or not in violation of the provisions of this
Section, Landlord may collect rent from the assignee; if the Leased Premises or
any part thereof are sublet to, or occupied by, or used by, any Person other
than Tenant, whether or not in violation of this Section, Landlord, after
default by Tenant under this Lease, may collect rent from the subtenant, user or
occupant. In either case, Landlord shall apply the amount collected to the rents
reserved in this Lease, but neither any such assignment, subletting, occupancy
or use, whether with or without Landlord's prior consent, nor any such
collection or application, shall be deemed a waiver of any term, covenant or
condition of this Lease or the acceptance by Landlord of such assignee,
subtenant, occupant or user as tenant. The consent by Landlord to any assignment
or subletting shall not relieve Tenant from its obligation to obtain the express
prior consent of Landlord to any further assignment or subletting. The listing
of any name other than that of Tenant on any door of the Leased Premises or on
any directory in the Building, or otherwise, shall not operate to vest in the
Person so named any right or interest in this Lease or in the Leased Premises or
be deemed to constitute, or serve as a substitute for, any prior consent of
Landlord required under this Section, and it is understood that any such listing
shall constitute a privilege extended by Landlord which shall be revocable at
Landlord's will by notice to Tenant. Neither an assignment of Tenant's interest
in this Lease nor a subletting, occupancy or use of the Leased Premises or any
part thereof by any Person other than Tenant, nor the collection of rent by
Landlord from any Person other than Tenant as provided in this subsection, nor
the application of any such rent as provided in this subsection shall, in

                                      -23-
<PAGE>

any circumstances, relieve Tenant from its obligation fully to observe and
perform the terms, covenants and conditions of this Lease on Tenant's part to be
observed and performed.

               16.  Default Provisions.

               (a)  Events of Default.  Each of the following events shall be
deemed to be, and is referred to in this Lease as, an "Event of Default":

               (1)  A default by Tenant in making any payment of Basic Rent or
Additional Charges on the date such payment is due and payable which continues
for more than five days after Landlord shall have given Tenant a written notice
specifying such default; or

               (2)  If, within any period of 12 consecutive months, Landlord has
given two written notices to Tenant pursuant to paragraph (1), a further default
by Tenant, within the 12-month period after the giving of the second such
notice, in making any payment of Basic Rent or Additional Charges on the date
such payment is due which continues for more than 10 days after such payment is
due; or

               (3)  The neglect or failure of Tenant to perform or observe any
of the terms, covenants or conditions contained in this Lease on Tenant's part
to be performed or observed (other than those referred to in paragraph (1)
above) which is not remedied by Tenant (i) within 20 days after Landlord shall
have given to Tenant written notice specifying such neglect or failure, or (ii)
in the case of any such neglect or failure which cannot with due diligence and
in good faith be cured within 20 days, within such additional period, if any, as
may be reasonably required to cure such default with due diligence and in good
faith provided that Tenant commences the curing of the same within the 20-day
period (it being intended that, in connection with any such default which is not
susceptible of being cured with due diligence and in good faith within 20 days,
the time within which the Tenant is required to cure such default shall be
extended for such additional period as may be necessary for the curing thereof
with due diligence and in good faith); or

               (4)  The assignment, transfer, mortgaging or encumbering of this
Lease or the subletting of the Leased Premises in a manner not permitted by
Section 15; or

               (5)  The taking of this Lease or the Leased Premises, or any part
thereof, upon execution or by other process of law directed against Tenant, or
upon or subject to any attachment at the instance of any creditor of or claimant
against Tenant, which execution or attachment shall not be discharged or
disposed of within 30 days after the levy thereof.

               (b)  Landlord's Rights Upon Event of Default.  Upon the
occurrence of an Event of Default, Landlord shall have the right, at its
election, then or at any time thereafter while such Event of Default shall
continue, either:

               (1)  To give Tenant written notice that this Lease will terminate
on a date to be specified in such notice, which date shall not be less than
three days after such notice if such notice is sent by registered or certified
mail, but which date may be the date of such notice or any date thereafter if
such notice is delivered in person, and on the date specified in such notice
Tenant's right to possession of the Leased Premises shall cease and this Lease
shall thereupon be terminated, but Tenant shall remain liable as provided in
subsection (c); or

               (2)  Without demand or notice, to reenter and take possession of
the Leased Premises, or any part thereof, and repossess the same as of
Landlord's former estate and expel Tenant and those claiming through or under
Tenant and remove the effects of both or either, either by summary proceedings,
or by action at law or in equity, without being deemed guilty of any manner of
trespass and without prejudice to any remedies for arrears of rent or preceding
breach of covenant.

                                      -24-
<PAGE>

               If Landlord elects to re-enter under paragraph (2), Landlord may
terminate this Lease, or, from time to time, without terminating this Lease, may
relet the Leased Premises, or any part thereof, as agent for Tenant for such
term or terms and at such rental or rentals and upon such other terms and
conditions as Landlord may deem advisable, with the right to make alterations
and repairs to the Leased Premises.  No such re-entry or taking of possession of
the Leased Premises by Landlord shall be construed as an election on Landlord's
part to terminate this Lease unless a written notice of such intention is given
to Tenant under paragraph (1) or unless the termination thereof be decreed by a
court of competent jurisdiction.  Tenant waives any right to the service of any
notice of Landlord's intention to reenter provided for by any present or future
law.

               (c)  Tenant's Liability for Damages.  If Landlord terminates this
Lease pursuant to subsection (b), Tenant shall remain liable (in addition to
accrued liabilities) to the extent legally permissible for (i) the sum of (A)
all Basic Rent and Additional Charges provided for in this Lease until the date
this Lease would have expired had such termination not occurred, and (B) any and
all reasonable expenses incurred by Landlord in reentering the Leased Premises,
repossessing the same, making good any default of Tenant, painting, altering or
dividing the Leased Premises, combining the same with any adjacent space for any
new tenants, putting the same in proper repair, reletting the same (including
any and all reasonable attorney's fees and disbursements and reasonable
brokerage fees incurred in so doing), and any and all expenses which Landlord
may incur during the occupancy of any new tenant (other than expenses of a type
that are Landlord's responsibility under the terms of this Lease); less (ii) the
proceeds of any reletting. Tenant agrees to pay to Landlord the difference
between items (i) and (ii) above with respect to each month during the Term, at
the end of such month. Any suit brought by Landlord to enforce collection of
such difference for any one month shall not prejudice Landlord's right to
enforce the collection of any difference for any subsequent month. In addition
to the foregoing, Tenant shall pay to Landlord, whether or not the Lease is
terminated, such sums as the court which has jurisdiction thereover may adjudge
reasonable as attorney's fees with respect to any successful law suit or action
instituted by Landlord to enforce the provisions of this Lease. Landlord shall
have the right, at its sole option, to relet the whole or any part of this
Leased Premises for the whole of the unexpired Term, or longer, or from time to
time for shorter periods, for any rental then obtainable, giving such
concessions of rent and making such special repairs, alterations, decorations
and paintings for any new tenant as Landlord, in its sole and absolute
discretion, may deem advisable. Tenant's liability as aforesaid shall survive
the institution of summary proceedings and the issuance of any warrant
thereunder. Landlord shall be under no obligation to relet the Leased Premises,
but agrees to use its best efforts to do so.

               (d)  Liquidated Damages.  If Landlord terminates this Lease
pursuant to subsection (b), Landlord shall have the right, at any time, at its
option, to require Tenant to pay to Landlord, on demand, as liquidated and
agreed final damages in lieu of Tenant's liability under subsection (c), an
amount equal to the difference discounted to the date of such demand at an
annual rate of interest equal to the then-current yield on actively traded U.S.
Treasury bonds with 10-year maturities, as published in the Federal Reserve
Statistical Release for the week prior to the date of such termination, between
(i) the Basic Rent and Additional Charges, computed on the basis of the then
current annual rate of Basic Rent and Additional Charges, which would have been
payable from the date of such demand to the date when this Lease would have
expired, if it had not been terminated, and (ii) the then fair rental value of
the Leased Premises for the same period. Upon exercise of this option by
Landlord and payment of such liquidated and agreed final damages, Tenant shall
be released from all further liability under this Lease with respect to the
period after the date of such demand. If, after the Event of Default giving rise
to the termination of this Lease, but before presentation of proof of such
liquidated damages, the Leased Premises, or any part thereof, shall be relet by
Landlord for a term of one year or more, the amount of rent reserved upon such
reletting shall be deemed to be the fair rental value for the part of the Leased
Premises so relet during the term of such reletting.

               (e)  Rights and Remedies Cumulative.  The rights and remedies
herein conferred are cumulative and not exclusive of any other rights or
remedies, and shall be in addition to every other right, power and remedy that
Landlord may have, whether specifically granted herein, or presently or
hereafter existing at law, in equity, or by statute.

                                      -25-
<PAGE>

               17.  Bankruptcy.

               (a)  Events of Bankruptcy.  The following shall be Events of
Bankruptcy under this Lease: (i) Tenant's becoming insolvent, as that term is
defined in Title 11 of the United States Code (the "Bankruptcy Code"), or under
the insolvency laws of any state, district, commonwealth or territory of the
United States (the "Insolvency Laws"); (ii) the appointment of a receiver or
custodian for any or all of Tenant's property or assets, or the institution of a
foreclosure action upon any of Tenant's real or personal property; (iii) the
filing of a voluntary petition under the provisions of the Bankruptcy Code or
Insolvency Laws; (iv) the filing of an involuntary petition against Tenant as
the subject debtor under the Bankruptcy Code or Insolvency Laws, which either
(A) is not dismissed within sixty (60) days of filing, or (B) results in the
issuance of an order for relief against the debtor; or (iv) Tenant's making or
consenting to an assignment for the benefit of creditors or a common law
composition of creditors.

               (b)  Landlord's Rights Upon Event of Bankruptcy.  Upon the
occurrence of an Event of Bankruptcy, Landlord shall have all rights and
remedies available to Landlord pursuant to Section 16; provided, however, that
while a case in which Tenant is the subject debtor under the Bankruptcy Code is
pending, Landlord shall not exercise its rights and remedies pursuant to Section
16 so long as (1) the Bankruptcy Code prohibits the exercise of such rights and
remedies, and (2) Tenant or its Trustee in Bankruptcy (hereinafter referred to
as "Trustee") (i) cures all defaults under this Lease, (ii) compensates Landlord
for monetary damages incurred as a result of such defaults, (iii) provides
adequate assurance of future performance on the part of Tenant as debtor in
possession or on the part of the assignee tenant, and (iv) complies with all
other requirements of the Bankruptcy Code.

               18.  Either Party May Perform the Other's Obligations.

               If Tenant shall fail to keep or perform any of its obligations as
provided in this Lease in respect to (a) maintenance of insurance, (b) repairs
and maintenance of the Leased Premises, (c) compliance with Legal Requirements,
or (d) the making of any other payment or performance of any other obligation,
then Landlord may (but shall not be obligated to do so) upon the continuance of
such failure on Tenant's part for 10 days after written notice to Tenant (or
after such additional period, if any, as Tenant may reasonably require to cure
such failure if of a nature which cannot be cured within said 10 day period), or
without notice in the case of an emergency, and without waiving or releasing
Tenant from any obligation, and as an additional but not exclusive remedy, make
any such payment or perform any such obligation and all sums so paid by Landlord
and all necessary incidental costs and expenses, including attorney's fees,
incurred by Landlord in making such payment or performing such obligation,
together with interest thereon from the date of payment at the Default Interest
Rate, shall be deemed additional rent and shall be paid to Landlord on demand,
or at Landlord's option may be added to any installment of Basic Rent thereafter
falling due, and if not so paid by Tenant, Landlord shall have the same rights
and remedies as in the case of a default by Tenant in the payment of Basic Rent.
If Landlord shall fail to keep or perform any of its obligations as provided in
this Lease in respect to (a) maintenance of insurance, (b) repairs and
maintenance of the Leased Premises, the Building or the common areas, or (c) the
making of any other payment or performance of any other obligation, then Tenant
may (but shall not be obligated to do so) upon the continuance of such failure
on Landlord's part for 10 days after written notice to Landlord (or after such
additional period, if any, as Landlord may reasonably require to cure such
failure if of a nature which cannot be cured within said 10 day period), or
without notice in the case of an emergency, and without waiving or releasing
Landlord from any obligation, and as an additional but not exclusive remedy,
make any such payment or perform any such obligation and all sums so paid by
Tenant and all necessary incidental costs and expenses, including attorney's
fees, incurred by Tenant in making such payment or performing such obligation,
together with interest thereon from the date of payment at the Default Interest
Rate, shall be paid by Landlord to Tenant on demand.

               19.  Security Deposit.

                                      -26-
<PAGE>

               (a)  Use and Application.  Tenant has deposited with Landlord the
Security Deposit, as security for the prompt, full and faithful performance by
Tenant of each and every provision of this Lease and of all obligations of
Tenant hereunder.  Landlord has invested the Security Deposit, and shall keep
the same invested, in (i) prime commercial paper, banker's acceptances or
certificates of deposit in United States commercial banks (having net assets in
excess of $100,000,000), in each case having a maturity of not more than 30
days, or (ii) obligations of the United States Government having a maturity of
not more than 90 days, or (iii) one or more mutual funds which invest their
assets primarily in investment of the type described in clauses (i) and (ii), or
(iv) one or more interest-bearing accounts in financial institutions the
deposits in which are insured by an agency of the United States.  If an Event of
Default occurs, Landlord may use, apply or retain the whole or any part of the
Security Deposit for the payment of (i) any Basic Rent or Additional Charges
which Tenant may not have paid or which may become due after the occurrence of
such Event of Default, (ii) any sum expended by Landlord on Tenant's behalf in
accordance with the provisions of this Lease, or (iii) any sum which Landlord
may expend or be required to expend by reason of Tenant's default, including
damages or deficiency in the reletting of the Leased Premises as provided in
Section 16.  The use, application or retention of the Security Deposit, or any
portion thereof, by Landlord shall not prevent Landlord from exercising any
other right or remedy provided by this Lease or by law and shall not operate as
a limitation on any recovery to which Landlord may otherwise be entitled.  If
any portion of the Security Deposit is used, applied or retained by Landlord for
the purpose set forth above, Tenant agrees, within 10 days after a written
demand therefor is made by Landlord, to deposit cash with the Landlord in an
amount sufficient to restore the Security Deposit to its original amount.

               (b)  Return of Security Deposit.  Provided that Tenant is not
then in default, the Security Deposit, or any balance thereof, and all accrued
interest or gains thereon, shall be returned to Tenant within thirty (30) days
after the expiration of the Term. In the absence of evidence satisfactory to
Landlord of any permitted assignment of the right to receive the Security
Deposit, or the remaining balance thereof, Landlord may return the same to the
original Tenant, regardless of one or more assignments of Tenant's interest in
this Lease or the Security Deposit. In such event, upon the return of the
Security Deposit (or balance thereof) to the original Tenant, Landlord shall be
completely relieved of liability under this Section.

               (c)  Return of Accrued Interest on Security Deposit.  Within
thirty (30) days after the execution of this Lease by both parties hereto,
Landlord will return all accrued interest on the Security Deposit to Tenant.

               (d)  Transfer of Security Deposit.  In the event of a transfer of
Landlord's interest in the Leased Premises, Landlord shall have the right to
transfer the Security Deposit to the transferee thereof. In such event, upon the
delivery by Landlord to Tenant of such transferee's written acknowledgment of
its receipt of the Security Deposit, Landlord shall be deemed to have been
released by Tenant from all liability or obligation for the return of the
Security Deposit, and Tenant agrees to look solely to such transferee for the
return of the Security Deposit and the transferee shall be bound by all
provisions of this Lease relating to the return of the Security Deposit.

               (e)  Restrictions on Encumbering.  The Security Deposit shall not
be mortgaged, assigned or encumbered in any manner whatsoever by Tenant without
the prior written consent of Landlord.

               (f)  Letter of Credit.  At any time during the Term, Tenant shall
have the right to deliver to Landlord a letter of credit in the amount of the
Security Deposit, to be held by Landlord as security for the performance by
Tenant of all of the obligations to be performed by it under this Lease. In such
event, Landlord shall refund the cash Security Deposit and all accrued interest
thereon to Tenant within fifteen (15) days after receipt of such letter of
credit. The letter of credit (and each replacement or renewal thereof) shall (i)
be irrevocable, (ii) be issued by NationsBank, N.A. or another national bank
having an office in Washington, D.C. or Fairfax County, Virginia, which has net
assets of $50,000,000 or more, (iii) be for a term of not less than 12 months
after the date of issuance, and (iv) authorize Landlord to draw thereon by a
sight draft delivered to the issuing bank accompanied by an affidavit of a
general partner, or executive officer, of Landlord that an Event of Default has

                                      -27-
<PAGE>

occurred and is continuing or that Tenant has failed to deliver a replacement
letter of credit within the time required by this subsection. Tenant shall, on
or before the 30th day before the expiration date of the letter of credit then
being held by Landlord under this subsection, deliver to Landlord an extension
or renewal of the letter of credit for a period of not less than 12 months.
Tenant shall extend or renew the letter of credit, or any extension or renewal
thereof, for successive periods of at least 12 months each throughout the Term.
Upon the occurrence of an Event of Default or the Tenant's failure to deliver a
replacement letter of credit within the time required by this subsection,
Landlord shall be authorized to draw on the letter of credit then being held by
it. Landlord shall receive, hold and apply the proceeds of the letter of credit
in the same manner and on the same terms as the Security Deposit. All references
in this Lease to the "Security Deposit" shall be deemed to include the proceeds
of the letter of credit.

               20.  Subordination.

               (a)  Mortgages.  This Lease and Tenant's interest hereunder shall
have priority over, and be senior to, the lien of any Mortgage made by Landlord
after the date of this Lease. However, if at any time or from time to time
during the Term, a Mortgagee or prospective Mortgagee requests that this Lease
be subject and subordinate to its Mortgage, this Lease and Tenant's interest
hereunder shall be subject and subordinate to the lien of such Mortgage and to
all renewals, modifications, replacements consolidations and extensions thereof
and to any and all advances made thereunder and the interest thereon. Tenant
agrees that, within 10 days after receipt of a written request therefor from
Landlord, it will, from time to time, execute and deliver any instrument or
other document required by any such Mortgagee to subordinate this Lease and its
interest in the Leased Premises to the lien of such Mortgage. If, at any time or
from time to time during the Term, a Mortgagee of a Mortgage made prior to the
date of this Lease shall request that this Lease have priority over the lien of
such Mortgage, and if Landlord consents thereto, this Lease shall have priority
over the lien of such Mortgage and all renewals, modifications, replacements,
consolidations and extensions thereof and all advances made thereunder and the
interest thereon, and Tenant shall, within 10 days after receipt of a written
request therefor from Landlord, execute, acknowledge and deliver any and all
documents and instruments confirming the priority of this Lease. In any event,
however, if this Lease shall have priority over the lien of a Mortgage, this
Lease shall not become subject or subordinate to the lien of any subordinate
Mortgage, and Tenant shall not execute any subordination documents or
instruments for any subordinate Mortgagee, without the written consent of the
prior Mortgagee.

               (b)  Ground Leases.  This Lease and Tenant's interest hereunder
shall be subject and subordinate to each and every ground or underlying lease
hereafter made of the Building or the land on which it is constructed, or both,
and to all renewals, modifications, replacements and extensions thereof. Tenant
agrees that, within 10 days after receipt of written request therefor from
Landlord, it will, from time to time, execute, acknowledge and deliver any
instrument or other document required by any such lessor to subordinate this
Lease and its interest in the Leased Premises to such ground or underlying
lease.

               (c)  First Mortgagee's Right of Cure.  If (i) the Building, or
any part thereof, or the land on which the Building is constructed, or the
Landlord's leasehold estate in the Building, is at any time subject to a first
Mortgage, and (ii) this Lease, or the Basic Rent and Additional Charges payable
under this Lease, is assigned to the first Mortgagee, and (iii) the Tenant is
given written notice of such assignment, including the name and address of the
assignee, then, in that event, Tenant shall not terminate this Lease or make any
abatement in the Basic Rent payable hereunder for any default on the part of the
Landlord without first giving written notice, in the manner provided elsewhere
in this Lease for the giving of notices, to such first Mortgagee, specifying the
default in reasonable detail, and affording such first Mortgagee a reasonable
opportunity to make performance, at its election, for and on behalf of the
Landlord.

               (d)  Non-Disturbance Agreement.  Notwithstanding the provisions
of subsections (a) and (b), neither this Lease nor any right, title or interest
of Tenant in the Leased Premises shall be subordinate to the lien of any ground
or underlying lease or any Mortgage made or placed after the date of this Lease,
and Tenant shall not be required to subordinate this Lease or Tenant's interest
in the Leased Premises to any such ground or underlying lease or any such
Mortgage, unless such lease or Mortgage contains an express provision (or the
lessor

                                      -28-
<PAGE>

or the Mortgagee or other party secured by the Mortgage agrees in writing) to
the effect that so long as this Lease has not been terminated by reason of the
occurrence of an Event of Default, the lessor or the Mortgagee (or other party
secured by the Mortgage) will be bound by all of the terms and provisions of
this Lease (except as otherwise set forth in such agreement), a default by the
Landlord under such lease or by the mortgagor under such Mortgage shall not have
any effect upon Tenant's right to occupy the Leased Premises in accordance with
all of the terms and conditions of this Lease, and the term, estate and options
of Tenant under this Lease shall not be terminated or otherwise affected by a
termination of such ground or underlying lease or a foreclosure and sale or
other action instituted under or in connection with such Mortgage.
Contemporaneously with the execution of this Lease, Landlord shall deliver to
Tenant a non-disturbance agreement, in form reasonably satisfactory to Tenant,
from the Mortgagee under any existing Mortgage, to the effect that so long as
this Lease has not been terminated by reason of the occurrence of an Event of
Default, the Mortgagee (or other party secured by the Mortgage) will be bound by
all of the terms and provisions of this Lease, a default by the mortgagor under
such Mortgage shall not have any effect upon Tenant's right to occupy the Leased
Premises in accordance with all of the terms and conditions of this Lease, and
the term, estate and options of Tenant under this Lease shall not be terminated
or otherwise affected by a foreclosure and sale or other action instituted under
or in connection with such Mortgage. Contemporaneously with the execution of
this Agreement, Landlord shall deliver to Tenant a non-disturbance agreement, in
form reasonably satisfactory to Tenant, from the lessor under the Ground Lease,
to the effect that so long as this Lease has not been terminated by reason of
the occurrence of an Event of Default, the lessor will be bound by all of the
terms and provisions of this Lease, a default by the Landlord under such Ground
Lease shall not have any effect upon Tenant's right to occupy the Leased
Premises in accordance with all of the terms and conditions of this Lease, and
the term, estate and options of Tenant under this Lease shall not be terminated
or otherwise affected by a termination of such Ground Lease.

               21.  Attornment.

               In the event of (a) a transfer of Landlord's interest in the
Leased Premises, (b) the termination of any ground or underlying lease of the
Building or the land on which it is constructed, or both, or (c) the purchase of
the Building or Landlord's interest therein in a foreclosure sale or by deed in
lieu of foreclosure under any Mortgage or pursuant to a power of sale contained
in any Mortgage, then in any of such events Tenant shall, at Landlord's request,
attorn to and recognize the transferee or purchaser of Landlord's interest or
the lessor under the terminated ground or underlying lease, as the case may be,
as Landlord under this Lease for the balance then remaining of the Term, and
thereafter this Lease shall continue as a direct lease between such person, as
"Landlord," and Tenant, as "Tenant," except that such lessor, transferee or
purchaser shall not be liable for any act or omission of Landlord prior to such
lease termination or prior to such person's succession to title, nor be subject
to any offset, defense or counterclaim accruing prior to such lease termination
or prior to such person's succession to title, nor be bound by any payment of
Basic Rent or Additional Charges prior to such lease termination or prior to
such person's succession to title for more than one month in advance. Tenant
shall, upon request by Landlord or the transferee or purchaser of Landlord's
interest or the lessor under the terminated ground or underlying lease, as the
case may be, execute and deliver an instrument or instruments confirming the
foregoing provisions of this Section. Tenant hereby waives the provisions of any
present or future law or regulation which gives or purports to give Tenant any
right to terminate or otherwise adversely affect this Lease, or the obligations
of Tenant hereunder, upon or as a result of the termination of any such ground
or underlying lease or the completion of any such foreclosure and sale.

               22.  Quiet Enjoyment.

               Landlord covenants that Tenant, upon paying the Basic Rent and
the Additional Charges provided for in this Lease, and upon performing and
observing all of the terms, covenants, conditions and provisions of this Lease
on Tenant's part to be kept, observed and performed, shall quietly hold, occupy
and enjoy the Leased Premises during the Term without hindrance, ejection or
molestation by Landlord or any party lawfully claiming through or under
Landlord.

                                      -29-
<PAGE>

               23.  Landlord's Right of Access to Leased Premises.

               (a)  Right of Entry.  Landlord and its agents shall have the
following rights in and about the Leased Premises: (i) to enter the Leased
Premises at all reasonable times to examine the Leased Premises or for any of
the purposes set forth in this Section or for the purpose of performing any
obligation of Landlord under this Lease or exercising any right or remedy
reserved to Landlord in this Lease, and if Tenant, its officers, partners,
agents or employees shall not be personally present or shall not open and permit
an entry into the Leased Premises at any time when such entry shall be necessary
or permissible, to use a master key or forcibly to enter the Leased Premises;
(ii) to erect, install, use and maintain pipes, ducts and conduits in and
through the Leased Premises which, when completed, will not substantially
interfere with the use or appearance or materially reduce the space afforded to
Tenant in the Leased Premises; (iii) to exhibit the Leased Premises to others at
reasonable times and for reasonable purposes; (iv) to make such repairs,
alterations or improvements, or to perform maintenance of all heating, air-
conditioning, elevator, plumbing, electrical and other mechanical facilities
installed by Landlord, as may be required from time to time by this Lease to be
made or performed by Landlord; (v) to take all materials into and upon the
Leased Premises that may be required in connection with any such repairs,
alterations, improvements or maintenance; and (vi) to alter, renovate and
decorate the Leased Premises at any time during the Term if Tenant shall have
removed all or substantially all of Tenant's property from the Leased Premises.
Landlord agrees to give prior notice before it exercises its rights under this
subsection, except that Landlord may enter the Leased Premises without notice in
the case of an emergency. In making such an entry, Landlord agrees to use
reasonable efforts to avoid interfering with the regular and usual conduct of
the Tenant's business. Notwithstanding anything to the contrary herein, Landlord
may obtain access to the double-secured areas of the Leased Premises only with
the permission and assistance of Tenant's Director of Facilities, except in the
event of an emergency posing a threat of immediate injury to persons or
property.

               (b)  Rights in Adjacent Areas.  Except as otherwise provided in
Section 10, all parts (except surfaces facing the interior of the Leased
Premises) of all walls, windows and doors bounding the Leased Premises
(including exterior Building walls, corridor walls, doors and entrances), all
balconies, terraces and roofs adjacent to the Leased Premises, all space in or
adjacent to the Leased Premises used for shafts, stacks, stairways, chutes,
pipes, conduits, ducts, fan rooms, heating, air-conditioning, plumbing,
electrical and other mechanical facilities installed by Landlord, service
closets and other Building facilities, and the use thereof, as well as access
thereto through the Leased Premises for the purposes of operation, maintenance,
alteration and repair, are hereby reserved to Landlord. Nothing contained in
this Section shall impose any obligation upon Landlord with respect to the
operation, maintenance, alteration or repair of the Leased Premises or the
Building.

               (c)  Effect of Landlord's Entry.  The exercise by Landlord or its
agents of any right reserved to Landlord in this Section shall not constitute an
actual or constructive eviction, in whole or in part, or entitle Tenant to any
abatement or diminution of rent, or relieve Tenant from any of its obligations
under this Lease, or impose any liability upon Landlord, or its agents, or upon
any lessor under any ground or underlying lease, by reason of inconvenience or
annoyance to Tenant, or injury to or interruption of Tenant's business, or
otherwise. Landlord agrees to exercise its rights under this Section in a manner
designed to minimize interference with Tenant's normal business operations,
without any obligation, however, to employ labor at overtime or other premium
pay rates.

               24.  Limitation on Landlord's Liability.

               (a)  Accidents, etc.  Except for damages resulting from the
willful or negligent act or omission of Landlord, its agents, employees or
contractors, Landlord shall not be liable to Tenant, its employees, agents,
business invitees, licensees, customers, guests or trespassers, for any damage
or loss to the property of Tenant or others located on the Leased Premises, or
in the Building or the land on which it is built, or for any accident or injury
to Persons in the Leased Premises or the Building, resulting from the necessity
of repairing any portion of the Building; the use or operation (by Tenant or any
other Person or Persons whatsoever) of any elevators, or heating, cooling,
electrical or plumbing equipment or apparatus; the termination of this Lease by

                                      -30-
<PAGE>

reason of the destruction of the Building or the Leased Premises; any fire,
robbery, theft, and/or any other casualty; any leaking in any part or portion of
the Leased Premises or the Building; any water, wind, rain, or snow that may
leak into, or flow from, any part of the Leased Premises or the Building; any
acts or omissions of any occupant of any space adjacent to or adjoining all or
any part of the Leased Premises; any water, gas, steam, fire, explosion,
electricity or falling plaster; the bursting, stoppage or leakage of any pipes,
sewer pipes, drains, conduits, appliances or plumbing works; or any other cause
whatsoever.

               (b)  Unavoidable Delays.  Neither Landlord nor Tenant shall be
required to perform any of its obligations under any provision of this Lease, or
be liable for loss or damage for failure to do so, nor shall the other party be
released from any of its obligations under this Lease because of such party's
failure to perform, where such failure arises from or through Unavoidable Delays
or Legal Requirements. If Landlord or Tenant is so delayed or prevented from
performing any of its obligations during the Term, the period of such delay or
such prevention shall be deemed added to the time herein provided for the
performance of any such obligation. Lack of funds shall not be deemed an
Unavoidable Delay for purposes of this Section 24(b), and nothing in this
Section 24(b) shall excuse Tenant's failure to promptly pay any Basic Rent or
Additional Charges due under this Lease, or Landlord's or Tenant's failure to
maintain policies or deliver certificates of insurance required hereunder.

               (c)  Building Services.  If Landlord shall fail to supply, or be
delayed in applying, any service expressly or impliedly to be supplied under
this Lease, or shall be unable to make, or be delayed in making, any repairs,
alterations, additions, improvements or decorations, or shall be unable to
supply, or be delayed in supplying, any equipment or fixtures, and if such
failure, delay or inability shall result from Unavoidable Delays, such failure,
delay or inability shall not constitute an actual or constructive eviction, in
whole or in part, or relieve Tenant from any of its obligations under this
Lease, or impose any liability upon Landlord or its agents by reason of
inconvenience to Tenant, or injury to, or interruption of, Tenant's business, or
otherwise, or entitle Tenant to any abatement or diminution of rent except as
provided in Section 3(i).

               (d)  Liability Limited to Landlord's Estate.  Notwithstanding any
provision to the contrary, Tenant shall look solely to the estate and property
of Landlord in and to the Building (or the proceeds received by Landlord on a
sale of such estate and property but not the proceeds of any financing or
refinancing thereof) in the event of any claim against Landlord arising out of
or in connection with this Lease, the relationship of Landlord and Tenant or
Tenant's use of the Leased Premises, and Tenant agrees that the liability of
Landlord arising out of or in connection with this Lease, the relationship of
Landlord and Tenant or Tenant's use of the Leased Premises, shall be limited to
such estate and property of Landlord (or sale, insurance or condemnation
proceeds in connection therewith).  No other properties or assets of Landlord
shall be subject to levy, execution or other enforcement procedures for the
satisfaction of any judgment (or other judicial process) or for the satisfaction
of any other remedy of Tenant arising out of or in connection with this Lease,
the relationship of Landlord and Tenant or Tenant's use of the Leased Premises,
and if Tenant shall acquire a lien on or interest in any other properties or
assets by judgment or otherwise, Tenant shall promptly release such lien on or
interest in such other properties and assets by executing, acknowledging and
delivering to Landlord an instrument to that effect prepared by Landlord's
attorneys.

               25.  Estoppel Certificates.

               Tenant and Landlord each agrees, from time to time, within 15
days after written request therefor by the other party, to execute, acknowledge
and deliver to the other party a statement in writing certifying to the other
party, any Mortgagee, assignee of a Mortgagee, or any purchaser, of the Building
or the land on which it is constructed, or both, or any other Person designated
by the other party, as of the date of such statement, (i) that Tenant is in
possession of the Leased Premises; (ii) that this Lease is unmodified and in
full force and effect (or, if there have been modifications, that this Lease is
in full force and effect as modified and setting forth such modifications);
(iii) whether or not there are then existing any set-offs or defenses known to
such party against the enforcement of any right or remedy of the other party, or
any duty or obligation of such party, hereunder (and, if so, specifying the same
in detail); (iv) the dates, if any, to which any Basic Rent or Additional
Charges have been paid

                                      -31-
<PAGE>

in advance; (v) that such party has no knowledge of any uncured defaults on the
part of the other party under this Lease (or, if such party has knowledge of any
such uncured defaults, specifying the same in detail); (vi) that such party has
no knowledge of any event having occurred that authorizes the termination of
this Lease by such party (or, if such party has such knowledge, specifying the
same in detail); (vii) the amount of any Security Deposit held by Landlord; and
(viii) any additional facts reasonably requested by any such Mortgagee, assignee
of a Mortgagee, purchaser or other Person.

               26.  Surrender of Leased Premises.

               (a)  Possession.  Tenant shall, on or before the last day of the
Term, except as otherwise expressly provided elsewhere in this Lease, remove all
of its property and peaceably and quietly leave, surrender and yield up to the
Landlord the Leased Premises, free of subtenancies, broom clean and in good
order and condition except for reasonable wear and tear, damage by fire or other
casualty, or conditions requiring repair by Landlord hereunder at Landlord's
expense.

               (b)  Inspection of Leased Premises.  At the time Tenant
surrenders the Leased Premises at the end of the Term, or within twenty (20)
days thereafter, Landlord and Tenant, or their respective agents, shall inspect
the Leased Premises and shall prepare and sign an inspection form to describe
the condition of the Leased Premises at the time of surrender.

               (c)  Survival.  The provisions of this Section shall survive any
expiration or termination of this Lease.

               27.  Holding Over.

               If Tenant shall hold over possession of the Leased Premises after
the end of the Term, Tenant shall be deemed to be occupying the Leased Premises
as a Tenant from month to month, at one hundred fifty percent (150%) of the
Basic Rent, adjusted to a monthly basis, and subject to all the other
conditions, provisions and obligations of this Lease insofar as the same are
applicable, or as the same shall be adjusted, to a month-to-month tenancy.

               28.  Mediation.

               In any case in which it is provided by the terms of this Lease
that any matter shall be determined by mediation, then such mediation shall be
in accordance with the Commercial Mediation Rules then in effect of the American
Arbitration Association ("AAA"). The mediation proceeding shall be conducted in
Washington, D.C., by one mediator selected by the AAA. The cost of the
mediation, including filing fees with the AAA and the cost of the mediator,
shall be borne equally by the parties. In the mediation sessions, the parties
shall endeavor in good faith to resolve the claim or controversy at issue. Any
party or the mediator shall have the right to terminate the mediation at any
time after the first mediation session. Neither party may make any disclosure of
the existence or results of the mediation without the prior written consent of
the other party. The mediator may not make any disclosure of the existence or
results of the mediation without the prior written consent of both parties. No
discussions in the mediation shall be admissible in any litigation between the
parties, and the mediator shall not be subject to subpoena to testify to any
communication between the mediator and either party. If the parties are unable
to settle the matter by mediation, then either party may submit such matter to
litigation.

               29.  Parking.

               Throughout the Term, Tenant shall be entitled to the use of 675
parking spaces in the structured parking facility for the Office Park (the
"Parking Spaces"), without additional charge therefor.  The Parking Spaces shall
be available to Tenant and/or its employees on an unreserved basis, in common
with the other tenants of the Office Park.

                                      -32-
<PAGE>

               30.  Renewal of Term.

               Provided that this Lease shall be in full force and effect and
that Tenant shall not then be in default, Tenant shall have the right, at
Tenant's sole option, to extend the Lease for one (1) consecutive additional
period of five (5) years (such additional period being hereinafter referred to
as the "Renewal Period", if exercised, and included in the definition of the
Term). Such option to extend shall be exercised by Tenant giving written notice
of the exercise to Landlord at least twenty-four (24) months prior to the
expiration of the Initial Term of this Lease. The Renewal Period shall be for
the same Basic Rent payable during the last Lease Year of the Initial Term,
escalated at the commencement of the Renewal Period and at the commencement of
each Lease Year thereafter by the Inflation Adjustment, and upon the same terms,
covenants and conditions set forth in this Lease with respect to the Initial
Term, and Tenant's obligations to pay Operating Expense Increases pursuant to
Section 3(b) shall continue without interruption during the Renewal Period. In
the event Tenant defaults beyond any applicable cure period under this Lease
after providing notice of exercise of its renewal option but prior to the
expiration of the Initial Term, such exercise shall, at Landlord's option
exercised by written notice to Tenant, be void ab initio.

               31.  Shuttle Service.

               Landlord shall provide for Tenant' s employees, other tenants of
the Building and other adjacent buildings owned by Landlord or its affiliates,
and the employees of such other tenants a private shuttle bus service between
the Building and the Vienna Metro Station. Subject to Unavoidable Delays, the
shuttle bus service shall be provided throughout the Term and continuously
during the hours between 7:00 a.m. and 8:00 p.m. on Business Days. Landlord
shall use shuttle buses which have reasonably adequate seating capacity taking
into account average passenger usage from time to time. Landlord shall provide
private shuttle bus service for Tenant's employees at times in addition to those
specified in this Section, at Tenant's expense, as mutually agreed upon by
Landlord and Tenant. Landlord shall charge Tenant for after-hours service at an
hourly rate from time to time established by Landlord, in its sole discretion,
but in no event will the rate per hour charged to Tenant be more than an amount
per hour which represents Landlord's reasonable estimate of its actual cost of
providing such after-hours service, including labor, cost of fuel, and wear and
tear on equipment, plus an allowance of 10% thereof to cover general overhead.
In the event the same after-hours service is also requested by other tenants of
the Building (or any other building owned by Landlord or its affiliates) in
addition to Tenant, the charge therefor to each tenant requesting such after-
hours service shall be a pro-rated amount based upon the net rentable area of
the leased premises of all tenants requesting such after-hours service. Payment
for such charges shall be due and payable to Landlord within 15 days after
Tenant's receipt of an invoice therefor. Any dispute between Landlord and Tenant
with respect to the adequacy of Landlord's shuttle bus service shall be
submitted to mediation pursuant to Section 28.

               32.  Leasing Commission.

               Landlord and Tenant each represent and warrant to the other that
neither of them has employed any broker, other than The Carey Winston Company,
in carrying on the negotiations relative to this Lease.  Tenant shall pay any
commission due The Carey Winston Company in connection with this Lease.
Landlord and Tenant shall each indemnify and hold harmless the other from and
against any claim or claims for brokerage or other commission arising from or
out of any breach of the foregoing representation and warranty.

               33.  Telephone Switch.

               Tenant intends, at its expense, to install a telephone switch in
the Office Space to provide telephone service to the Leased Premises. Subject to
agreement by Landlord and Tenant on marketing arrangements and other matters,
Tenant shall have the right to use its telephone switch to provide telephone
service to other tenants of the Building and any adjacent office building
located in the Office Park. Tenant hereby agrees to indemnify and hold harmless
Landlord from and against any and all claims, cases, actions, damages,
liabilities and

                                      -33-
<PAGE>

expenses (including attorneys' fees) that arise from or are in connection with
Tenant's provision of telephone services to other tenants.

               34.  General Provisions.

               (a)  Binding Effect.  The covenants, conditions, agreements,
terms and provisions herein contained shall be binding upon, and shall inure to
the benefit of, the parties hereto and, subject to the provisions of Section 15,
each of their respective personal representatives, successors and assigns.

               (b)  Governing Law.  It is the intention of the parties hereto
that this Lease (and the terms and provisions hereof) shall be construed and
enforced in accordance with the laws of the State of Virginia.

               (c)  Waivers.  No failure by Landlord to insist upon the strict
performance of any term, covenant, agreement, provision, condition or limitation
of this Lease or to exercise any right or remedy consequent upon a breach
thereof, and no acceptance by the Landlord of full or partial rent during the
continuance of any such breach, shall constitute a waiver of any such breach or
of any such term, covenant, agreement, provision, condition or limitation.  No
term, covenant, agreement, provision, condition or limitation of this Lease to
be kept, observed or performed by Landlord or by Tenant, and no breach thereof,
shall be waived, altered or modified except by a written instrument executed by
Landlord or by Tenant, as the case may be.  No waiver of any breach shall affect
or alter this Lease, but each and every term, covenant, agreement, provision,
condition and limitation of this Lease shall continue in full force and effect
with respect to any other then existing or subsequent breach thereof.

               (d)  Notices.  No notice, request, consent, approval, waiver or
other communication which may be or is required or permitted to be given under
this Lease shall be effective unless the same is in writing and is delivered in
person or sent by registered or certified mail, return receipt requested, first-
class postage prepaid, (1) if to Landlord, at Landlord's Notice Address, or (2)
if to Tenant, at Tenant's Notice Address, or at any other address that may be
given by one party to the other by notice pursuant to this subsection. Such
notices, if sent by registered or certified mail, shall be deemed to have been
given at the time of mailing.

               (e)  Entire Agreement.  It is understood and agreed by and
between the parties hereto that this Lease contains the final and entire
agreement between said parties, and that they shall not be bound by any terms,
statements, conditions or representations, oral or written, express or implied,
not herein contained. It is understood and agreed, however, that the terms
hereof shall be modified, if so required, for the purpose of complying with or
fulfilling the requirements of any Mortgagee secured by a first Mortgage that
may now be or hereafter become a lien on the Building, provided, however, that
such modification shall not be in substantial derogation or diminution of any of
the rights of the parties hereunder, nor increase any of the obligation or
liabilities of the parties hereunder.

               (f)  Jury Trial.  Landlord and Tenant each hereby waives all
right to trial by jury in any claim, action, proceeding or counterclaim by
either Landlord or Tenant against the other on any matters arising out of or in
any way connected with this Lease, the relationship of Landlord and Tenant
and/or Tenant's use or occupancy of the Leased Premises.

               (g)  Venue.  Tenant hereby waives any objection to the venue of
any action filed by Landlord against Tenant in any state or federal court in the
jurisdiction in which the Building is located, and Tenant further waives any
right, claim or power, under the doctrine of forum non conveniens or otherwise,
to transfer any such action filed by Landlord to any other court.

               (h)  Corporate Authority.  Concurrently with the signing of this
Lease, Tenant shall furnish to Landlord certified copies of the resolutions of
its Board of Directors (or of the executive committee of its Board of Directors)
authorizing Tenant to enter into this Lease; and Tenant shall also furnish to
Landlord evidence

                                      -34-
<PAGE>

(reasonably satisfactory to Landlord and its counsel) that
Tenant is a duly organized corporation in good standing under the laws of the
jurisdiction of its incorporation, is qualified to do business in good standing
in the State of Virginia, has the power and authority to enter into this Lease,
and that all corporate action requisite to authorize Tenant to enter into this
Lease has been duly taken.

               (i)  Time of the Essence.  Time is of the essence in the
performance of Landlord's and Tenant's obligations under this Lease.

               (j)  Gender.  Wherever appropriate herein, the singular includes
the plural and the plural includes the singular.

               (k)  Invalidity.  If any provision of this Lease shall be
invalid, illegal or unenforceable, the validity, legality and enforceability of
the remaining provisions shall not be affected thereby.

               (1)  Captions.  The captions in this Lease are for convenience
only and shall not affect the interpretation of the provisions hereof.

               (m)  No Partnership.  This Lease is not intended to create a
partnership or joint venture between Landlord and Tenant in the conduct of their
respective businesses.

               (n)  Counterparts.  This Lease has been executed in several
counterparts, but all counterparts shall constitute one and the same instrument.

               (o)  Deed of Lease.  To the extent required under applicable law
to make this Lease legally effective, this Lease shall constitute a deed of
lease.

               35.  Approval of Building Food Service Tenants.

               Throughout the Lease Term, Landlord shall not lease any space in
the Building to a food service tenant, or approve the transfer of any lease of
space in the Building to a food service tenant, without Tenant's prior written
approval of such food service tenant, which approval shall not be unreasonably
withheld, conditioned or delayed.

               36.  Termination of Prior Lease.

               This Lease entirely supersedes the Lease Agreement dated January
30, 1987, as amended by the First Amendment, the Second Amendment and the Third
Amendment, and the Lease Agreement dated January 30, 1987, as amended, is hereby
terminated.

               IN WITNESS WHEREOF, Landlord and Tenant have caused this Lease to
be signed by their duly authorized partners or officers as of the day and year
first above written.

                                        Landlord
                                        HMCE ASSOCIATES LIMITED
                                         PARTNERSHIP, R.L.L.P.

                                        By   /s/ David W. Evans
                                          -------------------------
                                        Tenant
                                        ICF KAISER HUNTERS BRANCH LEASING, INC.

                                        By   /s/ Timothy P. O'Connor
                                           -------------------------
                                        Vice President and Assistant Treasurer

                                      -35-